CMOS battery failed - how to replace it?

It's a CR 2032. You can buy a pack of two at wal-mart for 3 bucks:) It's the same battery they use in many of the passes for toll booths.

http://www.walmart.com/ip/Energizer-2032-3V-Lithium-Batteries-2-Pk./15988109

It's a CR-2032 battery.  Unplug the system, replace the battery and when you next power up, go into BIOS setup (F2) and turn off the floppy drive setting.  Verify that the hard drive is set in the boot list and save.

DL2032 or CR2032

Appendix - Documentation

Removing and Installing Parts <ADMIN NOTE: Broken link has been removed from this post by Dell>

Battery

Battery

Replacing the Battery

CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the Product Information Guide.

NOTICE: To prevent static damage to components inside your computer, discharge static electricity from your body before you touch any of your computer's electronic components. You can do so by touching an unpainted metal surface on the computer chassis.

A coin-cell battery maintains computer configuration, date, and time information. The battery can last several years. If you have to repeatedly reset time and date information after turning on the computer, replace the battery.

CAUTION: A new battery can explode if it is incorrectly installed. Replace the battery only with the same or equivalent type recommended by the manufacturer. Discard used batteries according to the manufacturer's instructions.

To replace the battery:

1. Record all the screens in system setup (see System Setup) so that you can restore the correct settings in step 9. <ADMIN NOTE: Broken link has been removed from this post by Dell>
   
   
2. Follow the procedures in Before You Begin. <ADMIN NOTE: Broken link has been removed from this post by Dell>
   
   
3. Remove the computer cover (see Removing the Computer Cover). <ADMIN NOTE: Broken link has been removed from this post by Dell>
   
   
4. Locate the battery socket (see System Board Components). <ADMIN NOTE: Broken link has been removed from this post by Dell>
   
   
5. Carefully press the battery release lever away from the battery and the battery will pop out.
   
   
6. Insert the new battery into the socket with the side labeled "+" facing up, then snap the battery into place.
   
   

1. Replace the computer cover (see Replacing the Computer Cover). <ADMIN NOTE: Broken link has been removed from this post by Dell>
   
   

NOTICE: To connect a network cable, first plug the cable into the network device and then plug it into the computer.

1. Connect your computer and devices to electrical outlets, and then turn them on.
   
   
2. Enter system setup (see System Setup) and restore the settings you recorded in step 1. Then go to the Maintenance section and clear the low battery and other errors associated with the battery replacement in the Event Log.
   
   
3. Properly dispose of the old battery.
   
   

See the Product Information Guide for battery disposal information.