Come across an irritating little bugger....

It prevents an xp system from booting into safe mode.
It prevents spybot from installing
It prevents AVG from installing
Adaware gives it a clean bill of health
mulit-av finds various viruses but claims to have deleted them
smitfraudfix doesnt find anything
Trend anti-virus when scanning causes a bsod
when installing the new avg antivirus the active shield wont run, and it
finds a not-a-virus.win32.realserver.b
causes a bsod when superantispyware is running
machine completely cleansed with hijack this....

Any ideas??

The trend online scanner found these:
adware bestoffers
adware_istbar
adware_funwebproducts
adware_bho_myway
adware_ibiswebsearch

Gaz