Task manager not back even after all the registry edits, deletion from window's system 32, and all the scans. There is still a program out there that has taken and highjacked your browser and windows. Boting in safe mode and doing several adware/spayware/viral scans is the only way to get it.
Best advice, update with the latest MS service pack and security updates is a sure fire way to keep it from coming back.
*Run a virus scan in safe mode
*Run an adware/spyware scan in safe mode
*Do a registry clean in safe mode
You are going to have to run several spyware/adware programs back to back (in addition to a virus scan.)
Start here
http://housecall.trendmicro.com (one of the best free/online adware/virus scans)
Then do a google search for "spybot search and destroy"
Finally download "Lavasoft ad-ware"
These should be used to supplement your base firewall and virus scan program.
You can run these in regular mode, but in some cases the scaning and deletion of System 32 files (while booted in regular windows) may cause your computer to freeze, crash, or the scanning program to lock up.
In addition most of these programs can not delete spyware/viruses that are running in the background. Since task manager is not working, you will have to go into ms confing to do a customized/selective windows start up in order to stop windows from automatically starting them. Anything that is not a window's function, stop it.
Finally here is some stuff I dug up that may help, it involves registry edits
http://windowsxp.mvps.org/Taskmanager_error.htm
http://www.pchell.com/support/taskmanagerdisabled.shtml