Try this:
Go into your Device Manager, and find your drive. Right click on it, and choose "Uninstall". After it uninstalls, reboot, and let Windows detect new hardware, and install new a driver for you.
Could also be that your drive went to PIO mode. It needs to be in DMA mode. Try this:
To ensure your drives are operating in DMA mode: (1) Control Panel, (2) System, (3) Goto the Hardware Tab, (4) Device Manager, (5) IDE ATA/ATAPI Controllers, (6) Right Click on Primary IDE Channel --> Properties, (7) Goto the Advanced Settings Tab, Make sure both drop down boxes say 'DMA if Available', Click OK,(8) Right Click on Seconady IDE Channel --> Properties, (9) Goto the Advanced Settings Tab, Make sure both drop down boxes say 'DMA if Available', Click OK, (10) Reboot.(Thanks to Praetor)
You might also want to see if there's a firmware upgrade for the drive, from Dell. If it's still under warranty, and you use a LiteOn firmware upgrade (even though it's a LiteOn drive), you will void your warranty. I thought Dell used Philips drives.....
Also, do you have AnyDVD? If so, make sure that DVD43 isn't on your computer. They are a conflict with each other.
Good luck!