Im currently using Mandrake 9.1 on a 200 mhz computer with 64mb of ram. I use kde 3.1 with no problems. It is by no means fast, but it runs decently for the old ass hardware. Plus high speed internet could make the slowest computer seem fast. Here is a small list of windows programs, with the linux alternatives that I use on my old machine.
Internet Explorer
Mozilla
Windows Media Player
Xine, Ogle, XMMS
Microsoft Office
Open Office
Easy CD Creator
E-Roaster, GCombust, CDrecord
Kazaa
LimeWire
mIRC
XChat
There are so many more as well that I didnt list. For games there are quite a few popular games that have linux ports, but for a lot of those that dont you can use WineX.
TheQuirk, he might not have a problem with the companies who right software for windows, he might just hate microsoft.