If you haven't installed it yet, I'd suggest trying WUBI - it's an installer that throws GRUB on your machine as a bootloader to dual-boot Windows and Ubuntu, and throws Ubuntu in a disk image that is mounted as the primary hard drive by GRUB when you fire up Ubuntu. That way, your Ubuntu partition is safely contained as a disk image on your Windows partition(s). Best of all, it's officially supported by the Ubuntu dudes. Grab it from http://www.ubuntu.com/download/ubuntu/windows-installer.
You'll want OpenOffice for Word/Excel/etc. compatibility, though I think that comes on the CD/DVD. Read over the WINE docs to learn how to get it all working - games seem to work well under WINE on Ubuntu these days.
And make sure you grab Chrome/Firefox/whatever and the latest Java JRE.
Feel free to hit me up on skype if there's anything specific you need help with.
@Hielor: Gaming under Ubuntu is not "seriously disappointing". Have you even tried it recently?
