Welome man,
2GB is plenty as Linux/Unix programs generally aren't as big as Windows. Do a search on the forum and you'll see some examples of other members partition setups, or you can just let the instllation program auto configure the system for you (Mandrake is good at this). If you'll not be using the machine as some sort of server, then you can probable forgo some paritions like /var. You may end up with something like:
/ 100MB (Boot part.)
/usr 1.1GB (programs, etc., like Windows 'Program Files')
/home 600MB (documents, like Windows 'My Documents')
/tmp 128MB (swap space)
The good thing is that you can share your 'My Documents' folder in windows as Linux will see it. So /home need not be too large leaving more space for program installs.
Hpoe this helps and good luck.