Virtual memory allows the system to use hard disk space to store information normally stored in RAM. Windows 7 and Windows Vista manages virtual memory by using a paging file. You specify the minimum and maximum size of this file. If the size is different from the default in Windows Vista, applications may return errors. However, some applications may require a non-default size for the paging file. Change the size only if other applications aren't adversely affected.
To set the paging file to the default size:
Note: You must be logged on as an administrator to change the size of the paging file.