Verified answer

Well if it's not booting, there's something wrong with your hardware. Getting a new power supply won't effect Windows at all. Try rechecking all the cables and hardware.

Most often, when a power supply suddenly dies...it will damage other components. Like the motherboard or hard drives in particular.*

Unfortunately, there is not enough information in your post for us to start to troubleshoot this. But if you say the computer comes on, I'll assume it POSTs OK. So most likely, your motherboard, CPU and new power supply are OK. If you're not loading windows 7 therefore, it is most likely a RAM or hard drive problem...

A new power supply won't prevent Windows 7 from starting. There must be something else wrong.

What is the error message you get?