even when you install on your d drive some adobe files must go on your c drive. if you don't have enough room on your c drive, you can't install on that computer.
Thanks for the explanation, so how much space would I need for photoshop? Is there anyway of changing which drive is the C: drive?
>anyway of changing which drive is the C: drive?
The C drive is what is used by Windows for Windows
Buy a bigger SSD and use a cloning program to clone your small drive to your new larger drive... and have the cloning program use the balance of the new drive as open space... then remove the old drive and connect the new drive in place of the old drive
ADDED Then make sure you set your programs to use your hard drive for temporary files, such as http://forums.adobe.com/thread/1007934?tstart=0 see reply 4