You can use your "run" command tool to check things out. If you click "start" and then "run" and then type "cmd" and then ok. The old dos screen will show and then type "sfc/scannow.exe" Which will allow Windows to verify that all protected Windows files are intact and in their original versions. Do this while offline and with no programs open. Take a pause from your machine as it will take about 30-45 minutes. When it is done, it will simply close back to your desktop. Then open the event viewer to see the results.
There is another tool you can run to check your hard drive for errors. Click "start' and then "my computer" then right click on your hard drive, usually "c" and then click "properties" and then "tools" and then check both boxes and then "ok." A dialog box will pop up saying 'it can not perform this task-ok to run at next start-up,' click "ok" and re-start your computer. A new screen will open saying a 'disk check' has been scheduled. Do not touch / do anything and it will start and run for about 15-20 minutes. It will then re-start again when completed and you will go to the event viewer for the results.
These tools will repair errors on your disc and insure system stability.
After all of this is done, open "system" located in the "control panel" and on the general tab it will list your 'ram memory installed.' Usually 256, 512 or 1024. It may show a number different, as some items will be using a little, round up to the closest number (496=512) write this number down and then click on the "advanced" tab and then the "performance settings." Next click "advanced" and then "change" under the vitural memory. Click "custom size" and then in both initial and maximun size, change the number to the number you wrote down-double the ram you have installed (if you have 256-enter 512, if 512-enter 1024)-then click "ok" and then "apply" and then "ok" and then "ok" on the system tab. Re-start your machine and all will be better.