Can i just add before doing anything and connecting to the net, look at the internet properties and see if it has a disconnect time activated, quite a few companys can set these themselves like bt.

If this all seems fine maybe look in your system 32 and other common folders used by the sys that a back door could have been stored in (if it is infact a hacker), run anti virus software incase there using a known trojen. The probabilaty that there using an im alert (if infact it is a hacker) is quite high. the server file will probably be named somthing like server.backdoor.bat if it is a silly trojen, for all you know it could be some one using buffer overflows and the works in wich case formatt back to 0 and install every thing again.

Or use somthing more stable like umm LINUX!
(joke)