1. Close any programs you are not using. If you are using the Windows Vista sidebar, be sure to close that.
2. Open up your task manager in Windows XP or Vista to see which running programs are using the most memory. Under the 'Process' tab will be a number of programs that are currently running on your computer.

3. Select 'View' and 'Select Columns'. In XP, check the box that reads 'Virtual Memory Size'; in Vista, it's the 'Commit Memory' option. This will display which programs are using the most virtual memory. Sort the column by size from largest to smallest. You can do this by pressing the column name.
4. Examine each program by name and usage. The longer a program is on without shutting down, the more virtual memory it will potentially use. If you are no longer using the program, end the process.
5. Consider re-installing or removing the ended programs all together. You should conduct an Internet search for any programs that you are unfamiliar with.
6. Run your start up menu program, which is commonly known as 'msconfig.' Select the 'Start up' tab to see which programs automatically run when you start up your computer. Deselect any programs you are familiar with that you may not actively use upon start, such as some toolbar or chat programs. Consider deselecting any programs you ended in Step 4. Re-boot your computer.