Vacuum cleaning is not recommended for delicate electronics. A vacuum cleaner can generate significant static electricity and if this discharges from the nozzle to a circuit board or chip, the chip internals can be destroyed. The recommended method, in normal circumstances, is to blow the dust out with canned air. Of course I can understand that you might not wish to blow the dust around the room. I usually do such things out in the garden, as typically there is a lot of dust when I get to the point of doing it.
On the other hand, although I have often seen the recommendation not to vacuum the interior of a PC, I have not actually had someone say they have destroyed a PC that way.
But on the other other hand, static damage doesn't always show immediately, but careful statistical analysis has been use to show that careless handling (in this case handling chips and boards by hand without wearing an earthed anti-static strap) does reduce the lifetime of electronic equipment. The point here is that lower level static discharges (you don't feel them) can do partial damage.
Personally I would advise against vacuuming, but I say that on the basis that I do not think I am mould sensitive. I'd recommend blowing out the dust with canned air out of doors unless that is too high a risk for you. If it is too much of a risk, then use the vacuum, but be aware of the risk to the electronics.
Also, if you do dismantle your PC, earth/ground your body. Either leave the case plugged into an earthed power socket, but switched off at the PC power switch and at the wall socket switch if there is one. The earth/ground lead is not switched. Then touch your hand against the metalwork of the case for a couple of seconds before touching the internal components. If you are removing them for later reassembly store them in antistatic bags if you have them available (it's the kind of thing I keep when I have them left over after installing new components. Another enthusiast might have some you could use).
An alternative is to use use the grounding in your home. In the UK at least, building regulations insist that metal pipework and so forth is attached to an earthing point. I'm assuming other developed countries have similar rules. Then for example you could do the work on a dry kitchen counter with the PC disconnected from the electricity supply. Then first before you touch any internals, equalise everything to remove static by holding the metal PC case with one hand and the sink (assuming it is steel) with the other so that it is all grounded before you start. Repeat the equalisation if you step away and return as the act of walking on certain floor coverings can generate static.
