I suggest installing ubuntu in may after the new 8.04 is fully released. It is a very nice OS.
I'd also suggest installing thunderbird (use their add/remove programs tool and search for thunderbird) because it will be closer to what you are used to in terms of mail client (and has good spam filtering). I think evolution is 'too complex' for most users. You will have firefox 2 and 3 (your choice, I think 3 is installed by default). Open office will handle most MS office documents. I'd suggest saving new documents (but not existing documents) in the open office format and exporting to PDF (built in) when you need to send the file to someone who does not have open office.
So to revamp,
I'd install ubuntu 8.04 when it comes out this month.
The first thing I would do is use the restricted driver manager (which will show up in the taskbar) to install 3rd party drivers for your video card (this will give you 3d support).
Then, I would go into the applications menu to add/remove applications and install thunderbird, I think it is better then evolution for simple email.
Next, I would use the same tool to install vlc, this will allow you to playback almost any file except encrypted dvd's. That requires you to install another library (libdvdcss). There will be tutorials on that in the ubuntu wiki when hardy is released.
At this point you have:
web: firefox (also on windows)
email: evolution or thunderbird (also on windows)
video: vlc (also on windows)
audio player: Rhythmbox (kinda itunesish, I prefer amorak, you can install that again via add/remove programs)
office: open office (also on windows)
chat: pidgin (also on windows, supports all major chat platforms)
bittorrent: transmission (also on mac, very nice program imho)
and that just scratches the surface. You will probably be able to install 99% of what you need via either add/remove applications or synaptic (a more advanced program for install applications). I usually use gimp, bluefish, and a few others on my default installs.
if you have an application, and want to know a good linux replacement, ask and I'll see what is out there.