Computer Case

I would leave them alone. I have alot of vents on my htpc case, but they serve a purpose. Fresh air has to come in from somewhere and since your temps are fine, there's no need to cover the vents. You can always sell the case and start over, but sometimes components don't work after transferring them over to a new case. I would just wait for your next build to change anything. If you're still worried about dust, get some canned air with solvent; I get mine on sale two for $5 at frys.

why do you need canned air with solvent? what are you trying to dissolve?

OP: if you're concerned about those you can try positively pressurizing your case (more intake than exhaust) which will force the air to leave through those vents rather than come inside.

But as oldie said, if you aren't having problems with cooling, I don't see any point plugging them up. If you're seeing a large amount of dust sticking to those openings, you can try to cover them up and see how things go, but point is if you got negatively pressurized case, and those are your only intake vents then you'll start pulling dust from all the other little cracks, that is a lot harder to get a handle on than a vent in an accessible location that you can easily clean.

Well I guess I'll cover them with masking tape and see if the CPU temp goes up. The thing is all the pc I ever had never had all these side slots, except for the 1 side vent/hole for the CPU.+
I believe it sucks in to much dust.

you could slap a filter on it, you know

Excellent idea, glad I thought of it. LOL Thanks