virus problem on lan

I have problem of folling viruses
namely:-
1.w95/lorez.1766
2.win32/dupator
3.l-worm/opas.l
4.l-worm/opas.a
5.l-worm/opas.e
6.l.worm/opas.k
these viruses cause my lan slow
they load themselves on windows startup
and cause my lan speed slow and come so many warning message
please tell me what i do with these viruses
i occour this problem on so many places
please give my solution for that
i shall be highly thatk ful to you