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You could boot into safe mode and attempt to delete them. Hopefully they won't be running while your computer is in safe mode, therefore you will be able to delete them.
- Restart your computer
- Repeatedly hit the F8 key while your computer is starting
- Choose Safe Mode when prompted
You may also be able to run your antispyware and antivirus software in safe mode with success.
If after doing this you continue to have issues, I would suggest posting a HiJackThis log in the HiJackThis forum here at Bleeping Computer. Instructions on how to do this can be found HERE