This Registry mod is only one of a bizillion possible changes that can cause problems.
Since you don't know the name of the virus or the changes that Spyware Terminator made it may be that your only reasonable option is to reinstall the OS. Dell usually supplies (or offers to supply) a system restoration CD that is used to do this. If you did not get this CD with your system go to the Dell site and inquire how you can get this. Typically the CD is around $10.
Be sure to write down the Service Tag number from the sticker on the back of the machine. Call Sales at the number shown here:http://support.dell.com/support/topics/glo...;l=en&s=dhs
Be sure to tell them you want the disc for XP, not Vista.
If you do reinstall the OS, beforehand you may wat to do a data backup to a removeable drive while your system is operational (and before it crashes again).