1.) Choose which drive bay you want to install the drive and remove the face plate off of that bay. Save the face plate for future use. Pick a bay that will fit the drive. If you have to install a 3.5" drive in a 5.25" bay, you'll have to use a special front panel to adapt it. This panel usually comes with a new floppy drive. 

2.) Fit the drive into the bay without connecting anything. Just make sure it fits. Choose the best possible fit. 

  3.) Connect the ribbon cable and the power supply to the drive. If you just removed a floppy drive, just use the same connections. If not, study the available connectors. You should have a ribbon cable with a twist on one end. The end without the twist is attached to the floppy controller. Then, attach the connector after the twist to floppy drive A:. If you have only one floppy drive, then it is Drive A:. You may have two available connectors after the twist. Use the one that fits your drive. One is for 5.25" drives, the other is for 3.5" drives.

 
  4.) If you are using brackets to hold the drive in place, secure them now. You may need to temporarily disconnect the cables. Once in, tighten the drive in place. Double-check the connections, also checking the connections for other drives to make sure you didn't bump one out of place. 

  5.) Now put everything back together. Plug the system in. And turn it on. If the floppy drive light goes on and stays on, this means that one of the connectors of the ribbon cable are on backwards, meaning Pin 1's are not aligned. Find which is not aligned and flip it. If you get a Floppy Drive Fail (40) error, it probably means the same thing...either that or the system is looking for a drive which is not there, in which case move on to step 6 and adjust the BIOS settings. 

  6.) Now you have to tell the computer that it has another drive. This involves updating the BIOS. Boot the computer and enter setup. This is done by pressing F1, Del, Ctrl-Alt-Esc, or some other combination. Your computer will tell you what keys to hit right after you turn it on. After entering setup, go to the Standard Setup, usually the first menu option. Your main floppy drive is A: . Any second floppy drive is labeled B:. Using the appropriate keys, activate your new drive. You may need to type in the specs for the new drive. Most likely, it is a 1.44MB drive. Lastly, under another menu option, you might need to make sure your BIOS drive swapping is turned off. This feature, through BIOS, reverses the order of your floppy drive letters so that their location in relation to the ribbon twist does not matter. But, if you installed a drive after the twist, and this option is enabled, your Drive A: will not work.
To deactivate a drive you have removed, follow the same instructions, but change the status of the drive to "None" or "Not installed." If you have removed the primary floppy drive, you'll need to change the Boot Order to "C: Only" and disable Floppy Drive Seek. 

7.)  When you are done adjusting BIOS, save the new setup, then exit Setup. Your system should now restart and your drive will be activated. You can test it in the Explorer or File Manager by checking a diskette.

Removing Floppy Drives 

1.)  Turn the computer off, take the case off, and remove any diskettes from the drive. 

 2.) Locate the disk drive. This should be pretty easy for most of us. 

3.) Now go about disconnecting the drive. Remove the screws that fasten the drive to the support casing, then unplug the power source from the back of the drive. Also remove the ribbon cable. As you do all this, keep track of what goes where so that you can put it all back correctly. If you had a 3.5" drive in a 5.25" drive bay, you may have to remove some brackets too. 

 4.) You are now ready to install a new floppy drive. Skip down to this section to see how. If you do not plan on replacing the one you took out, go on to step 5. 

 5.) You now need to cover up the drive bay with a plastic panel. You may already have one that fits the drive bay, but if not you can pick one up at a retail computer shop. 

 6.) Next you need to remove the drive from the system's BIOS so that it doesn't think its really there. Enter Setup, choose the first option, called "Standard CMOS" or something like that. Then, in the section on the floppy drive you removed, change the option to NONE or DISABLED. Save and Exit.