-Make sure there's at least 32MB of memory installed.
-Remove and reinsert all memory modules, making sure that they are firmly seated.
-If there's more than 1 memory module, try starting up with only one module installed at a time. If the system fails to start up, then replace the bad module.
-Go to Start/Run, type msconfig, click OK/Advanced, make sure the box for 'Limit memory to....' is unchecked.
-Repartition, reformat, and reinstall Windows.