. You should upgrade your RAM, 1.5GB is barely sufficient for most applications, you should have at least 2GB
Depends on what you are going to be running. If you're going to treat this machine like XP, I would just disable a bunch of the unnecessary system processes and services with msconfig, it'll drastically speed things up. If you want to game on it or play any resource heavy programs (maya, photoshop, etc...), I'd definitely get more RAM. Otherwise aim for somewhere between 30-50 processes running (you can check with Task Manager). But aside from that, if this is a laptop, I wouldn't use it for gaming anyway.