Always include the version of Windows in your posts.
Could have been a RAM problem if you got 4 beeps and you seem to have resolved that by reseating the modules. But the RAM error may have caused some corruption to a file on the hard drive.
Assuming the diagnostics pass, you can reboot and press F8 before Windows starts to load. Select Last Known Good. If that gets you to the desktop without errors, shut down normally and reboot normally, and you should be good to go.
You may also want to run chkdsk on the hard drive:
Click: Start>run
Type in: chkdsk C:
Click OK
Accept the offer to run chkdsk at next boot and then reboot. chkdsk will run before Windows loads. It may take a long time, depending on size of your hard drive, so be patient.