What are you looking to tweak? Boot time? Available memory? I recommend that you read up on the .NET Server services and you can selectively enable and disable as you see fit.
 
As for the web server, IIS in .NET is locked down pretty tight, so you'll have to be fairly certian of what you're doing in order to get it working properly.
 
As far as TweakXP and related programs, I personally dislike these, I would rather learn how to make adjustments to the system with the OS tools, such as Regedit, etc. Once I have found a registry setting that performs as needed, I often export it and add it to a .reg file, that way when I rebuild the OS next time, all I have to do is merge the .reg file with the registry.

True, I only use the server for web and game server now. I moved to apache as for webserver since it works much better with php. Boy was that a speed improvement
 
I have tweak the services but it still consumes a lot of memory. Much more that 2k server.

What consumes more memory? Just so you know, the major trend for large-scale applications (even moreso with MS apps) is to let them take all available memory, and then they will release memory back to the system if requested by the OS, and it isn't needed by the app. While Exchange 5.5 is a good example of this behavior running poorly, SQL Server 2000 does this quite well. In addition, many apps can be tuned either through wizards (like Exchange 5.5 and SQL) or reg tweaks/metadata mods (like Exchange 2000). If you hit technet and search for memory consumption with respect to a given application/service, there might be an article or two on it detailing what needs to be done.

and memory is SO cheap now a days - especially if u still got pc133 or lower - just go buy more
 
heck - even DDR is fairly cheap as well.