User guest turns on by itself and virus setup.exe

[armeniomanuel]

hello. i have some troble with wingate machine(xp) for some time: 4 or 5 computers on the network have a Trojan rizalof and the wingate machine also has it. in all machines the virus is in the foler "c\documents and settings\all users" and has the name setup.exe.
NOTE: All the machines have static ips and i ALWAYS have the user "Guest" disabled but sometimes it turns on by itself...One of the infected machines goes online with is own ip adress and simultaniously with that "guest ip". i think that machine is infectig my wingate machine...20-30 times a day..The users in my network dont need to autenticate but i put the properties for user Guest in the www.proxy to need autentication. have i done ok..?? why does the user guest enables it self..? how can i put this more secure..?
thanks again.

[armeniomanuel]

one more note: i have kaspersky for wingate instaled and it never sems to find this setup.exe alias trojan rizalof on the wingate server. its my antivirus panda that detects it...
and more interesting....if i make a scan trough the network from a computer with kaspersky instaled it detects it again like in panda...strange..
:S