Tip - Block Write Access To Run and RunOnce Registry Entries - Rectified.
Blocking write access to Run and RunOnce registry entries for malware or other unwanted programs running in the system.
Your system becomes unstable because of the malware programs running in the background. You identify these programs and kill them in the Task Manager but these programs will re-appear in the Task Manager after you reboot the system. This is because these programs will run again from the below mentioned registry keys:
Read more here...
http://www.windowsnetworking.com/kbase/WindowsTips/WindowsXP/UserTips/Boot/BlockWriteAccessToRunandRunOnceRegistryEntries.html