Verified answer

Scan for viruses

Scan for ad-ware [if your virus program doesn't, you'll need to download a program for this -- i use ad-adware Se - this is free]

Scan for spy ware [if your virus program doesn't -- i use spy bot - there's a free version of this]

First run the Disc Cleanup in accessories

Then go to Uninstall Programs and make sure you don't have programs on it that you don't use, if you're unsure about a program don't touch it

The run disc fragmenting also found in accessories.

Don't download from suspicious sites, such as adult sites. Visiting them is enough to mess up your computer.

Practice safe Hex :D

Its probably loaded with malware, download, update and scan with Spybot and Adaware besides your AV program. If you have been downloading a lot of stuff esp videos etc, its likely fragmentation has spread over the drive like an epidemic, and together these can literally pull a PC down to its knees. Run a diskcleanup and analyze the drive for fragmentation.

Using a registry cleaner can clean up your computer and then make your computer faster,Why?the reason is that there may be some regsitry errors and remnant,corrupt files and temp files in your computer to cause "computer slow".

Everytime you install and uninstall software on your computer and surfing online you create junk in the computer registry.over time, the registry can grow to enormous proportions, especially if the various programs you've installed do not do a good job of deleting and/or updating it's Registry entries.You need to scan and clean your computer with registry cleaner to make it fast.Good Regisry Cleaner will improve your computer and Internet performance dramatically!It even can speed up your computer by 300% or more!

There are some comparison and review of TOP 5 registry cleaners.

http://www.speeduppc.info/

You can download and scan your computer for free.

Check http://www.pc-optimizer-pro.com/

With pc optimizer pro you can safely clean, repair and optimize your computer.

It will help improve your system performance.

Good luck!

you have 2 choices if you dont have access to upgraded hardware:

1. tweak your existing setup

or

2. reinstall your operating system and start from scratch

the following assumes you are using windows xp

Ive included a 'quick sketch' below, followed by some links whch will explain in more detail.

the most basic starting point is to just clean up your pc's hard disk.

Go to "Start", "All Programs", "Accessories", "System Tools", and then select "Disk Cleanup". Under the "Disk Cleanup" tab check all the boxes except; "Compress old files" and "Catalog files for the Content Indexer", then select "OK" and "Yes" to perform these actions.

You could also remove unused programs (control panel > add/remove). Its pretty much ok to remove anything you're familiar with and are confident you wont need to use in future. Wise to stay clear of anything you're not _completely_ sure about.

ccleaner is an excellent application thats free, and assisst with system cleanup:

http://www.ccleaner.com/download/builds

next, run a spyware checker. if you dont already have one, you might like to try~ http://www.spywareterminator.com/ or

http://www.lavasoft.de/software/adaware/

Once you've done this, you could through your hard drive and remove any large files you no longer need. You could also have a look through your email client (if you use one) and sort your old emails by size. once youve done this, delete any with large attachments which you no longer need.

Now defrag your hard disk. Start/programs/accessories/disk defragmenter

with that done you may want to check your registry for redundancies and errors. If you dont already have a registry cleaner you might like to try~

http://personal.inet.fi/business/toniarts/ecleane.... or

http://www.eusing.com/free_registry_cleaner/regist...

you could then defrag your page file and registry (standard defrag does not achieve this - a step often overlooked in tune-up literature)

http://download.sysinternals.com/Files/PageDefrag....

It may be worth checking each hard drive with 'scandisk'. there are other issues such as lost clusters and bad sectors that the defragmentation utility cannot touch. It's a good idea to run XP's built in error checking utility on your drives every 2-3 months. This utility will scan your disks for errors and optionally attempt to correct them.

Open 'My Computer' from the desktop. 'Right-click' on your main hard drive, (usually 'C:'). Select 'properties' then 'tools' and under 'error checking' select 'check now…'. Check both 'Automatically fix file system errors' and 'Scan for and attempt recovery of bad sectors'. Restart your machine. 'Scandisk' will run during startup and can take a while depending on the size of your drive.

Thats the hard disk taken care of.

From here there are a number of tweaks you can apply. there just isnt space here to go into all the options. Detailled links are below.

The basics:

Before doing anything here, if you have a disk imaging program like norton ghost, make a backup of your operating system. If you dont have a setup like this, at the very least, activate a system restore point. To access the System Restore Wizard, click Start, and then click Help and Support. Click Performance and Maintenance, click Using System Restore to undo changes, and then click Run the System Restore Wizard.

Creating a restore point can be useful any time you anticipate making changes to your computer that are risky or might make your computer unstable.

- if you are running a licensed copy of xp make sure that windows update is activated. to manually run it ~

Open Windows Update in Help and Support Center.

On the Windows Update home page, click Scan for updates.

Click Yes when prompted to install any required software or device drivers

- trim down your computer's start-up files. at the very least edit start menu/programs/startup folder to remove any software that does not have to be run every time your computer starts up

- you can take this further by start/run/msconfig -> startup and editing the programs that are activated when windows starts. Be careful not to remove anything here that you are unsure of.

- clean out your Scheduled Tasks folder. Go to C:\Windows\Tasks, and delete the shortcuts of any programs that you don't want to run automatically on a schedule.

- go to your system tray (task bar r/hand side) and see whats running. If there's anything there you're confident doesnt have to be on, right click it and find the program's preferences/options. set the program so that the program doesnt start automatically at windows start up.

- Turn off Windows Animations and Visual Effects. From the Control Panel, click on the "System" icon. Click on the Advanced tab. Click the "Settings" button underneath "Performance". Uncheck the options related to animations, and other un-needed visual effects.

- if you have more than 500 fonts installed on your computer, remove some. excessive fonts in xp can make a big negative difference to performance. To do this, from the Control Panel, click on the "Fonts" icon. You can delete the fonts you don't use here. keep the basics: Verdana, Arial, Times, Trebuchet, Courier, serif, sans-serif, Georgia, etc...

- Disable 'file indexing'

The 'Indexing service' extracts information from documents and other files on the hard drive and creates a "searchable keyword index." This process can be quite taxing on any system. Windows XP's built-in search functionality can still perform these searches without the Indexing service. It just takes longer.

Open 'My Computer' from the desktop. 'Right-click' on your main hard drive, (usually 'C:'). Select 'Properties'. Uncheck 'Allow Indexing Service to index this disk for fast file searching'. Then select 'Apply changes to C:, subfolders and files', then select 'OK'. If a warning or error message appears (such as 'Access is denied'), select the 'Ignore All button'.

malware removal

http://mywebpages.comcast.net/SupportCD/MalwareRem...

registry tweaks

http://www.tweakxp.com/performance_tweaks.aspx

General tweaks

http://www.tweakhound.com/xp/WindowsXP.htm

General maintenance software (achieves much of the above in one package)

http://personal.inet.fi/business/toniarts/ecleane....

Finally, you might like to give you computers internals a clean. Switch off, open case and gently brush away any dust/debris from inside. make sure all fans are free of dirt and are rotating freely. be careful not to impact anything, especially small wires (power switch, usb, etc) on the motherboard which can easily detach.