This might be of use to some people out there experiencing the same problem running Allied Assault in Windows 7.
Recently I installed Windows 7 Ultimate 32bit and had major ping/lag issues. Tried all things that I could find and today it seems like there's a solution. Not by myself, but over here in that very first post.
Basically the solution is:
Open regedit
Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile
There will be an entry for network performance throttling, default value is 10; set it to FFFFFFFF hex (willl look like 0xFFFFFFFF to the right of the entry)
Reboot