Assuming you have Windows XP and you have a Windows XP CD you can try the following ..
First go to "C:\WINDOWS\SYSTEM32" and look for a file named
"wpa.dbl" back that up to a floppy or burn it to a CD-R.
This file will allow you to copy and paste it back to "C:\WINDOWS\SYSTEM32" when you are done with the repair process so that you are not forced to re activate Windows or call Microsoft to re install your legal copy of Windows.
If you have your Windows XP CD and you have the serial key then you are good to go.
You need a Windows XP CD to repair the registry and core system files. You would change your systems BIOS boot order to CD-ROM first and place your Windows XP CD in. Reboot system and allow it to load from the XP CD. You may need to hit any keyboard key when prompted to allow the XP CD to load.
Now keep going through the screens until you see your partition listed on the screen. Do not select it. Just hit "R" on your keyboard to start the repair process.
Allow the files to be re installed and continue with the installation until it's completed. Once the system is done with that part and it wants to restart you need to go back into the BIOS and change your boot order again to the hard drive first then floppy ect... Sometimes it won't be labeled hard drive it may be labeled IDEO or IDE1 in the BIOS.
Ok once that is set save it and exit the BIOS. Reboot and allow the installation procedure to continue. When it asks for the CD KEY to continue just hit cancel and allow it to continue. Just keep clicking next next ok ok until your are done.
This procedure will not format the system but if you had some applications that were also corrupted or were located in the system or systems32 directory they may need to be re installed.
Once this procedure is completed you should be able to boot up the system without the spyware issues. You should still run a scan on your entire drive to check the other directories which are not part of the core files.
Lastly, if it loads up and it says you can't login until you activate Windows, would you like to activate now - ignore that and reboot into safe mode. Simply copy and paste the WPA.dbl file I told you to backup at the beginning into "C:\WINDOWS\SYSTEM32" and reboot again. Allow the system to load and it should allow you to log in without a problem.
If it doesn't you will need the key so that is why you should know the serial key to the XP CD you will be using to do the repair procedure.