Over to the D drive?

You cannot really 'switch' to drive D. All you can do is to save everything that comes in the future in the drive D. Unless you really really want to save in drive C which I wouldn't recommend.

Most, if not all of the programs on your computer, runs on the C drive and if ever it crashes, you'll lose everything on that drive. If you save your data on drive D, when the computer crashes, you will only have to re-install the programs and software.

I don't know however what would happen if you change the physical drives of the computer. My guess is that many programs will fail to run properly since all of them are in the C Drive and will look for addresses starting at C. (which is now in D since you switched the drives... )

Thank you for your answer. I was kind of afraid that might be the case. When I realized the C drive was filling up, I did start to save things to the D drive. Right now, the C drive has about 400 MB of space and the D drive has 95 GB. Thanks again.