Does having 3 folders on desktop slow my computer down? See screenshot

No. Not even thirty.

If these are actual files and not just aliases, then yes if you are still running Leopard.

Performance tip: Keep the Desktop clutter-free (empty, if possible)

Mac OS X's Desktop is the de facto location for downloaded files, and for many users, in-progress works that will either be organized later or deleted altogether. The desktop can also be gluttonous, however, becoming a catch-all for files that linger indefinitely.

Unfortunately - aside from the effect of disarray it creates - keeping dozens or hundreds of files on the Desktop can significantly degrade performance. Not necessarily because the system is sluggish with regard to rendering the icons on the desktop and storing them in memory persistently (which may be true in some cases), but more likely because keeping an excessive number of items on the Desktop can cause the windowserver process to generate reams of logfiles, which obviously draws resources away from other system tasks. Each of your icons on your desktop is stored as a window in the window server, not as an alias. The more you have stored, the more strain it puts on the window server. Check your desktop for unnecessary icons and clear them out.

Keeping as few items as possible on the Desktop can prove a surprisingly effective performance boon. Even creating a single folder on your Desktop and placing all current and future clutter inside, then logging out and back in can provide an immediately noticeable speed boost, particularly for the Finder.

And it is why Apple invented 'Stacks'.

This no longer applies to Snow Leopard and later. I think you intended to mean that, but then it wasn't altogether clear that most of your post was intended for Leopard and earlier. 🙂

I know, but this is the Leopard forum, and I am sure I mentioned Leopard, so until the OP tells us he is not actually running Leopard, my note carries relevance. 🙂

Its relevance was never in question.