pagefile.sys is usually 1.5 to 3 times the size of your real RAM. You have to experiment to find out what is optimal. Basically, the more programs you have loaded that are not actually doing anything, the bigger pagefile.sys should be. In Vista you control the size of it with Start ⇒ Control Panel ⇒ System and Maintenance ⇒ System ⇒ Advanced System Settings ⇒ Advanced⇒ ⇒ Performance ⇒ Settings ⇒ Advanced ⇒ Virtual Memory ⇒ Change. If you had 2Gb of RAM, you might set the size of pagefile.sys to 3000 MB.

For good performance, you want pagefile.sys contiguous on disk, not scattered all over the disk in a number of fragments. You don’t want the disk arms to go chasing all over since this is a very heavily used files. pagefile.sys can’t be defragged like an ordinary file; it takes special techniques. See the defragger entry on programs to do that for you. Even they fail sometimes, so here is a technique for manual defragging:

Manual Defragging of pagefile.sys

Let us say you had two partitions C: and D:. First create a pagefile.sys on D:. Then reboot. Then set the size of the one on C: to 0. Then reboot. Then defrag C:. Then set the size of the C: pagefile.sys back to normal. Then reboot. Then set the the one on D: to 0. Then reboot. Windows will then recreate the pagefile.sys in the vast empty spaces freed on C:, and it will natually create it in one piece, right after the end of the files, (which if you have use O&O defragger with the COMPLETE ACCESS option, are nicely in order so the most active files are at the end close to the newly created pagefile.sys).