stealth virus on explorer.exe

Hello all,
I have a computer infected with a virus that act like this:
explorer.exe start opening smtp connections to several ip's and url's
until it exceed the tcp limit of windows xp sp2.
If I kill explorer.exe and run again from task manager the virus doesn't
run anymore until reboot.
It seems that the booting process of windows pass a parameter to
explorer for launch the virus. But not found anything interesting or
clear in the registry or boot.
I used nod32 and panda active scan for cleaning with no result. I alsoo
used spybot, adaware and superantispyware with the same null result.

Any ideas?

Thanks

-- 
Isaac Perez Moncho 
GSEC, SSP-GHD, SSP-MPA, SSP-CNSA Microsoft MCP.
JPL TSolucio S.L
www.tsolucio.com


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