When you run MSCONFIG, Registry Editor (regedit) or Task Manager, they flash for a second and quit.

This symptom is caused by Viruses. These three

are important system utilities which the viruses target.

A quick method is to rename the files and run them.

Extracting new copies of these files with the same name may

not help. Rename these utilities and run them or download this program

from the link

http://www.dougknox.com/xp/utils/xp_emerutils.htm
(NOTE: Your anti-virus software may warn of a potentially
malicious script. This is normal, as the Windows Scripting
Host is used to create the "copies" of these 3 utilities)

This program creates usable copies of MSCONFIG, REGEDIT AND

TASK MANAGER
and it copies to following place: C:\EmergencyUtils folder.

now u can run the msconfig, task manager, and registry editor