Is that really true? Back when I was a little more obsessed with having the smallest possible partition for my Windows XP operating system, I would create another partition specifically to install programs to. Let's say I have partitions C, D and E. C is Windows XP, D is where I install stuff to, and E is where I download stuff to.

So I would start out and let's say I'm looking for image editing stuff. I would go download GIMP to the E drive. Then I would double click on the exe in the E drive and when it asks me where I want to install it, I would install it to D:\GIMP.

It always ran fine from within Windows XP. So is there some reason that installing on a partition other than the partition that Windows is installed on a bad idea?