Windows failed to start. A recent hardware or software change might

Hi All,

 

I'm using a dell computer with windows Vista installed in it and it's running slow. A friend of mine advised me to download and install Norton Power Eraser and Norton 360 to make my computer in a good and fast running condition. i followed and Used NPE, ran it through Safe Mode with Networking, deleted the suggested files, boot it up through the Normal mode and installed N360 trial version. After intalling N360 and restarted my computer, it gave me the error: 

 

Windows failed to start. A recent hardware or software change might be the cause.
To fix the problem:

1. Insert your Windows installation disc and restart the computer.
2. Choose your language settings and click next.
3. Click "repair your computer"

 

it also gives me options for:

 

Safe Mode
Safe Mode with networking
Safe Mode with Command Prompt
Last known good configuration
Start Windows normally

 

I plugged in my Windows vista installer and booted from CD but its not working, after i Press any key to boot from CD, it goes back to the same page where it says Windows failed to start.

 

I also tried using the Safe modes and Last known good configuration and Start Windows normally but after i click on these, it gives me a blue screen saying:

 

STOP: Error 02c0000000x

 

I searched Google and found a work around by using the Norton Bootable Recovery Tool, burned it to a cd, boot from cd but still I end up with the screen STOP: Error 02c0000000x.

 

I dont want to reformat my computer since there are so many important files there and i can't lose it. please help me with this.