As a side note, your 2 instances of one file is not an error in w2k. Each user account has their own settings and files which is located in C:\Documents and Settings for w2k.
If you have a copy of program.exe on the desktop for both admin and guest, then you have two copies of it on your C: drive. However, you can put the file into C:\Documents and Settings\All Users\Desktop and there will only be one copy that is accessible by all who use that computer.
Lastly, there is a great free program that I use which gives you a graphical representation of what files are taking up the most room on your hard drives. It's called scanner.exe (not too original) and it works well. Just download, unzip to a directory, and hit the scanner.exe.
You can get it
here.
Wedo