About as much as all those programs on your pc. Why not use a seperate 'Gamer' account? That's what I've done. All my games are installed on the one account along with Teamspeak and all other related programs. Runs sweet as a nut.
Bahhh.. having other programs installed doesn't slow your PC when gaming unless they are running.. or in the taskbar idle or something.
Shortcuts on the desktop doesn't slow it down either. Having more than one account on a PC will slow it more than that- especially HD speed, and especially if you don't tweak the services that start up and run.
Why bother? I don't have many games on my HD or too many shortcuts on my desktop. Before I had loads and it was noticable, what I have on there now are my "essentials". I have attached what I was on about, my old PC used to be similar to that.
IMO What you have done with accounts is overcomplicate things really and as BWX232 said, accounts slow you down.
I'm one of the clean-guys! But I haven't seen anyone have his taskbar this way. People think it's weird and not comfortable, while it actually took me like a minute to get used to, and I get confused when I get somewhere that isn't like this. I have everything that I need, easy to find, and I can read the date very well, I don't need anything more
*Don't know how it happend, but I think I forgot the attachment