I have two machines for gaming, one is my "Legacy" gamer, and my newer one.
My Legacy gamer has an Intel VC820 Motherboard with a Pentium III Coppermine 1Ghz socket 370 processor on a Slot1 conversion board. It has 512Mb of RDRAM and a nVidia FX5200 AGP with 128Mb and 4 Hard Drives, the games running from the D: drive to free up system seek times on the C: drive. The OS is Windows 98SE and I can run IL-2 1946, but it's slow and not worth it. Otherwise I can run all the Legacy games/sims from the late 80's onwards. Just about all the games/sims are set to maximum (except IL-2 1946)...
My newer gamer has a MSI MS-6558G motherboard with a Pentium 4 Northwood 2.4GHz socket 478 processor. It has 2 Gb of SDRAM and an ATI X1650 AGP Pro video with 512Mb DDR3 and 2 Hard Drives. All the games also run off the D: drive to free up the seek time on the C: drive. This machine has XP Pro for the OS, and I have a number of the more recent games/sims onboard. All the games/sims on this machine are set to thier maximum as well.
By the way, if you're running low on Virtual Memory, you can either increase the VM in your system's settings (as long as you have enough room on your current HDD), or you can add a second Hard Drive and allocate the VM to it's own partition.