Windows Vista and 7 support ReadyBoost which will use a fast USB drive as a cache for SuperFetch. This allows SF to work better on systems with limited RAM. This can help increase responsiveness of file I/O operations because the flash drive is much faster at 4K random read/writes than the HDD.
Better yet, get a SSD drive. A pagefile on an SSD is really fast and will improving paging operation speeds fairly significantly, but is in no way a replacement for more RAM.
BTW, have you attempted to install larger RAM than it the motherboard suggests that it can use? It's possible that if you upgrade to the latest BIOS revision that you might be able to use larger chips, such as 2x2GB or 4x1GB (not sure how many RAM slots you have). It shouldn't hurt to at least try a larger chip if you have one available.
Also, you should reduce the RAM allocation to your virtual machine to as little as is needed to run the VM. An XP guest can run in as little as 256MB or 384MB of RAM depending on what you're using it for.
5No and no. You need to disable everything you can (services, prefetch, indexing, etc.) to free up RAM. Using XP could make your life easier. – mtone – 2012-01-01T06:23:01.030
3@kobaltz RAM disks take free memory to use as a drive, which is the opposite of what OP is asking. I don't think a "disk RAM" (as opposed to a "RAM disk") utility is possible. And to add about why virtualbox doesn't do it: virtualization is a sort of gateway to your system, not a emulator. – mtone – 2012-01-01T06:40:01.640
3Should probably think about getting another motherboard. . . – surfasb – 2012-01-01T11:02:45.043
1Honestly Nate, this system is NOT made for virtualization, more as a kitchen computer, if you need this for work or study you're better of building or buying a 400$ 'normal' pc. Otherwise, I'd recommend dualbooting instead of virtualization! and @surfasb: Getting a different motherboard is not really the option on a hp slimline – HTDutchy – 2012-01-01T11:32:31.970
@s4uadmin: That brings up a good point. That powersupply would not hold up even if you did plug in a more powerful motherboard. – surfasb – 2012-01-01T11:40:47.010