If you choose to install a Linux distro on your computer, you will usually get an office suite (usually OpenOffice, which is 99% compatible and 100% capable), a plethora of media apps such as Amarok, K3b CD/DVD utility, and on and on, plus equivalents to Windows' miniapps, such as KolourPaint for MSPaint replacement, Calculator, Dictionary, blah blah blah...and then a truckload of admin apps AND development tools. However, you can install everything or install just the bare minimum, up to you. And, you can add and remove later if you want.
If you do install a Linux distro such as Fedora Core 8 or Ubuntu, have at least 512MB ram, a 20GB (who has these anymore???) to however big your hard drive is, a Pentium III or better (aim for a P4) and the usual bare minimum DVD ROM drive. These are bare minimums, I would aim for higher. I have a 2GHz AMD Athlon 64 X2 cpu, 2 GB RAM, 200GB hard drive, and a DVDRW drive, and this thing is a speed demon! I only bought it for less than $650 (w/o monitor)