I will assume by C drive and D drive you mean two different partitions on the same hard drive.
BACK UP YOUR DATA. BACK UP YOUR DATA. BACK UP YOUR DATA.
If this goes wrong all the data on the affected partitions could be lost.
Got that out of the way. Now, don't use a partition manager, just use the one that comes with Windows, it works fine.
On the Start menu type "disk management". Click "Create and format hard disk partitions".
Now, on to the numbers. There is no amount you need to have on either as long as there is still a little free space (just a buffer, like 8 MB). If you want to move 70 GB of free space from partition D to partition C, do so. If you want to move 40 GB of free space, do so.
The question is, how much free space do you need?
If you know how much space you want to move from D to C, right click on D: in the disk management window. Click "Shrink Volume". Type the amount of space you want to take away from partition D to partition C in the "Amount of space to shrink in MB" box. (Note: 1 GB roughly equals 1000 MB, but exactly equals 1024 MB if you need to be exact.)
After it is done, right click on your C: partition and click "Extend Volume". I haven't done this step in a while and couldn't do it on my computer, so all I can say is follow the instructions to the best of your knowledge. (Could someone chime in on this please?)
After this you will have moved free space from partition D to partition C. Good luck, and don't forget to back up your data first.
There is currently 7.87GB free space in my C Drive. There is 70.8GB free space in my D Drive.
Now, I want to add more free space to the C Drive.
I am using a partition manager to do this.
Now, how much free space should be in the C Drive, and how much free space should there be in the D Drive?
Please give me the exact amount.
I have a desktop, Dell Windows Vista Home Basic.
I don't download a lot. I just upload a lot of pictures, videos to my computer. And music.