Faster RAM is only going to give you marginal performance gains, if any at all, and even if it does you won't notice it. What sticks do you have? If you have 2x1GB and 2x512MB then it's not worth buying new memory since you can have these in dual-channel, but if you have 3 1GB sticks you could buy a set of identical sticks for dual-channel, though it still isn't going to give any significant performance gains.
To disable pagefiles,
1. Go to system properties
2. Go to "Advanced" tab
3. Under the "Performance" section, click "Settings"
4. Go to "Advanced" tab
5. Under the "Virtual Memory" section, click "Change"
6. For all drives that have a page file on them, check "No Paging File" and click "Set"
7. Press OK, Reboot, and you should be set
This is the procedure for XP Pro but if I remember correctly it's pretty much the same for Vista.