Why not use 64-bit Ubuntu?
When I tried to download Ubuntu, I have two options : 32bit and 64bit, and 32bit is recommended. Is there any reason for this?
The 32-bit version of Ubuntu will run on most modern computers, but 64-bit has more specific requirements. There are a few things that won't run well with the 64-bit version (although these don't seem to be many), so the 32-bit version is recommended just to cover all the bases, I think. However, if you have a 64-bit computer, odds are that everything you need will run on it and will do so very well.
For example, I was able to get the Linksys AE1000 wireless access point to work just fine with my 32-bit Ubuntu, but when I changed to the 64-bit version I could no longer get the AE1000 to work. (Perhaps there's a fix but I was never able to find it.) However, that wasn't a big deal for me, and overall the 64-bit version feels a bit faster and it really runs everything else I've tried.
And although the 64-bit version is called AMD, it works as well on Intel 64-bit processors.