I suggest
Linux-Mandrake It is easy to install. If you want to have windows and linux on your computer, you will have to duel boot. When installing Linux, mandrake will come with a partitioning program that runs in the install (its called DiskDrake). You have to have a swap partition, and another partion for the actual OS. Your Swap partition is the same as virtual memory in windows, it should be about twice what your memory is (mine is 200MB, i have 80MB of RAM). Your second partition will have to be at least 2 GB (if your not planning on installing anything else) But i am using an 18GB partion for mine. For the Linux partion you can choose between a few different types, the main two are Ext.2 and Ext.3. I am using Ext.3, they are both pretty much the same except Ext.3 can recover data easier in the case of a power outage or sudden shutdown.
If you are duel booting with windows already installed, you will have to setup LILO (the bootloader) to load windows off whatever partition its on (Mandrake install should do this for you).
As for the GUI i recommend using KDE.
thats pretty much it for now. Anybody else want to share?