I've partitioned the hard drive into three partitions:
C: Windows
D: Swapfile (used by Windows as a temporary storage space)
E: Applications

Always install new applications to E: drive. Always store documents, photos, music, etc. (basically everything) on E: drive.
You'll find that when you try to install applications, they normally default to C:/Program Files
always look for a 'Custom' or 'Browse' button near the start of the installation process, and use that to navigate to E:/Applications, then install the application there, such as:
E:/Applications/Winamp

I have made two 'images' of C: drive at various stages of the Windows installation:
1: Basic Windows installation without Windows updates loaded
2: Basic Windows installation with all drivers installed, and all Windows updates installed.
These images are saved on the E: partition of your hard drive, but also backed up to DVD+R, so you're doubly safe!

I can re-install an image file in about four minutes. If in the future you find the PC is running slowly, or gets stuck like your old one did, all we have to do is re-install image no. 4, and it will be exactly the way it was when you first got it. But you will need to reinstall any new applications you have loaded since receiving the PC, but all your photos, music, etc. will still be untouched on E: drive. (That's why you should put everything like that on E: drive).