Aha- I think we're starting to see the violence inherent in the system. Your video card should be fine- given what you're attempting to play that should suffice. But silverai hit it on the head talking about 32 bit programs and 64bit operating systems- Battlefront was designed with 32bit OSes in mind, not 64. The LucasArts page for it doesn't even make mention of Vista. Mechwarrior 3 is even older, and can at times have issues with XP. I think Vista is not backwards compatible enough to run it.

Second Life... well let's just say there's a fairly solid chance it isn't your computer that's at fault when that gets slow. Based on my limited experience with it, things can get pretty bad pretty quickly just due to their servers being strained.