32-bit Ubuntu or 64-bit w/Intel Atom D510 w/4GB RAM?

Solution 1:

64 bit.
1. Yes. Only the following apps are 32bits (all runs with 32bit cross libs) (64bit were always "ready" on Linux. Only few proprietary things are not really supported natively. But loading 32bit libs when it needs, takes only 1-2 secs every occasion (I mean every time you boot your machine and have to load a Skype, it'll have to fetch the 32bit libs. Windows does this at boot or load I guess.):
- Skype
- Flash main 32bit plugin
- Acrobat Reader
2. Yes it plays. 64bit (which we just call 64 bit) was called AMD64 and later other manufacturers (Intel) adopted it. Intel got an own 64 arch, called IA-64, however that is a different story (those are high-end servers).
3. 64bit.