If you remove the old drive and install the new drive, the number of drives in your PC does not change and drive letters are not changed. However, if you add a second hard drive to your PC, most likely one drive letter will change.
For example, before you had a hard drive C and a CD-ROM drive D. After adding the new drive, your PC will assign the letter D to the extra hard drive and move the CD-ROM drive letter up one so that you now have a hard drive C, a hard drive D, and a CD-ROM drive E.
Of course this is normal and there is nothing wrong with this order. But please note that you may have to reinstall some programs (only the ones that don’t run after this procedure) that run from the CD-ROM drive, as the drive letters are now shifted. As an example, if you installed Quake II on your PC when the CD-ROM was the D drive, Quake now expects you to insert the program CD into drive D every time you want to play the game. However, after the drive letter shift the CD-ROM is E, but Quake will still look in D.
There are some programs out there that supposedly can search your registry and configuration files and change any reference to the D drive to point to the E drive instead. But due to some bad experiences with these types of programs we recommend that you rather reinstall the application on top of itself from the CD as this method is much safer.
Links to Hard Drive Manufacturers
Below are links to the most popular hard drive manufacturers where you can find documentation for your specific hard drive including the correct jumper settings.
– Grogan/Alex –