If you poke around tip sites, you'll find a lot of myths and harebrained theories about optimizing virtual memory (the hard-disk space Windows uses to supplement your RAM)--a few of them even perpetuated by me. This time I went to the horse's mouth for the Microsoft-approved ways to set Windows' memory management to full steam ahead.

If you have only one hard drive, just leave well enough alone. But if you have two or more internal or external hard drives (not just disk partitions), your PC will be peppier if you keep the default paging file (what Microsoft calls the virtual memory disk space) on your boot drive (the one that holds Windows) and add a paging file to the second drive.

To do so, log in to Windows as an administrator and verify that you have more than one hard drive in your computer: Click Start, Run (just Start in Vista), type diskmgmt.msc, and press <Enter> to open the Disk Management utility (click Continue in the User Account Control, if necessary). The bottom pane shows each disk on your system and the drive letter that corresponds with each partition. To have only one new paging file, choose the fastest drive you have. Remember that an internal drive will be faster than an external drive in most cases. Note the drive letter(s) you'll use.

Now right-click My Computer (Windows 2000 and XP) or Computer (Vista) and choose Properties. In Windows 2000 and XP, select the Advanced tab; in Vista, pick Advanced system settings in the task pane on the left.

Bonus tip: In Vista, you can open the System Properties dialog box directly to the Advanced tab by clicking Start, typing systempropertiesadvanced, and pressing <Enter>. As with the preceding method, you may have to click Continue in the User Account Control dialog box.

In the Performance section, click Settings (Performance Options in Windows 2000) and then the Advanced tab (in XP and Vista). Under Virtual Memory, click Change. In Vista, uncheck Automatically manage paging file size for all drives. You'll see a paging file size already listed on your Windows drive; leave it alone, or Windows won't be able to create a memory dump file with debugging info in the event of a particular type of system error.

Next, in the drive list select a partition on a different drive where you want to add another paging file. Select Custom size if you want to set the size yourself and type in the initial and maximum size (Microsoft says making them the same amount is most efficient); Microsoft's rule of thumb is to make the file 1.5 times the amount of RAM in your system. Or select System managed size to let Windows determine the size (XP and Vista only). Click Set, then OK.

If the partition you selected contains another installation of Windows, you'll receive an error message warning that the file pagefile.sys already exists there. As long as the two operating systems are not running at the same time using virtualization software, it's safe for you to overwrite or delete pagefile.sys, since Windows will re-create the file automatically the next time you boot that partition's Windows installation.

You'll see a reminder that the changes will take effect the next time you restart your system. Windows will most often use the paging file on the least-busy drive, which means your new paging file will do most of the work.

Send Windows-related questions and tips to scott_dunn@pcworld.com. We pay $50 for published items. Scott Dunn is a contributing editor for PC World.