Unregister option won't appear by default either in 2000/XP. To unregister this DLL, use the following command:
regsvr32 /u dllfilename. First, open Command Prompt and goto the folder where this file resides. Then run the command 'regsvr32 /u GAMsys.dll' without quotes.
As suspected, this DLL adds into Internet Explorer as a Browser Helper Object with a name "IE 4.x - 5.x Adware Server" and with it's GUID {F36C1198-FC6B-4012-9928-DFA76FB56CC3}
For immediate relief, get ToolbarCop from here:
http://www.mvps.org/sramesh2k/toolbarcop.htm
In the right-pane BHO section, disable the entry "{F36C1198-FC6B-4012-9928-DFA76FB56CC3}"
BTW, the DLL module does not give much information except it's name "IE 4.x - 5.x Adware Server".