When you start an application, its files are copied into your computer’s RAM, which is the quickest way for the PC to access the data. However, the RAM may not always have enough space for the application’s needs, so Windows will allocate a portion of the hard drive as virtual memory—called a page file.

Because data transfers from the hard drive more slowly than it does to RAM, virtual memory is only used when the memory modules are full. However, if the page file is too small, Windows may need to frequently swap out the data, which can significantly slow down your PC. Alternatively, a page file that’s too large may allow Windows to write large files to the hard drive, and the extra hard drive activity will also slow down your PC. In general, it’s best to let Windows control the size of the page file. However, by default, Windows only creates page files on the drive where Windows is installed. If you have two (or more) hard drives on your computer, you can speed up the PC’s ability to retrieve data by allowing Windows to create page files on all your hard drives.

To access the page file settings in WinXP, right-click My Computer, click Properties, select the Advanced tab, and click the Settings button under the Performance heading. Choose the Advanced tab, select the Change button under the Virtual Memory heading, choose the drive where you want to create a paging file, and click the System Managed Size radio button. If you’d prefer to set the page file size, Microsoft recommends that the size of the paging file is one and a half to three times the amount of RAM on your computer. Repeat the process for any other drives on your PC.

In Vista, click Start, right-click Computer, and choose Properties. Select Advanced System Settings from the left-hand pane and click the Settings button under the Performance heading. Select the Advanced tab and click the Change button under the Virtual Memory heading. Click the Automatically Manage Paging File Size For All Drives and click OK. You’ll need to restart your PC before the OS applies the page file alterations.