To increase system performance it is highly recommended to setup a fixed size for your swap file.
To do that click on Start --> Control Panel --> System --> Advanced --> click on Settings under the Performance tab --> Advanced --> click on Change under the Virtual Memory tab. Now select the drive where Windows is installed and then select "Custom size". Set the "Initial size" and "Maximum size" to two times your actual physical RAM size. For example if you have 128 MB RAM type in 256. Now click on OK tree times.