Fdisk

You can only easily move data files to the D: drive.

You can actually move the My Documents folder to the D: drive.
You can change the file location for most programs to use the drive of your choice.

As for downloads, you can direct them to ANY drive or folder of your choice.

To add more room to the C: drive, you would need to use a partition manager utility such as Partition Magic. This assumes that you have 1 physical drive that is divided into 2 partitions.
If you have 2 physical drives, there is NO way to add more capacity to the C: drive.

Caution: Even though problems don't happen often with Partition Magic, it is "best" practice to back up your files before changing your partition structure.

The only "practical" way to move your installed programs to D: is to uninstall them and then reinstall to the D: drive.

If you have 2 physical drives, you might be able to copy the C: drive to the D: drive and swap the drives around.
I have not tried this on a XP system.
In the past, I have done this on Windows 98 systems.
I used the utility from the hard drive manufacture and choose to copy the old drive onto the new drive.
CAUTION: you will loose any files on the D: drive if you do this.
After copying the files, you need to make sure that the drive becomes a bootable volume.
Then, change the jumpers to make the 62GB drive the master, and the 8GB the slave.

Chas