I am looking into the possibility of supplying headless terminal servers to customer so that they can run a specific, single application via terminal services.

This would solve many of the potential problems that getting my clients to run my software would bring up. BY using terminal services it doesnt matter whether they are an XP, Vista or Linux environment as they all have Remote Desktop Clients that wok with Terminal Services. I would simply have one box to maintain that could be completely pre-configured before shipping allowing the clients complete plug & play installation.

Some clients are single users, some are 4 or 5 to an office and some have ten offices with 4 users in each location.

My question is, how do I know how big or small a Terminal Server I need?
Is there a "realistic" minimum spec for the TS plus X amount of RAM/Disk Space per user?

Ideally I would have three box sizes available for 1-5, 6-10 and 10+ users but so far I can't seem to get a handle on the OS requirements other than what Microsoft say themselves and they still say 128Mb RAM is OK for running XP!!!!!!

Any help would be greatly appreciated.