Message "CPU fan failed", why and how to fix?

Hi all,

I have 4+ year old homebuild that I would like to keep using as an extra computer... today I got a message about the CPU fan failing (coupled with an odd buzzing noise from the box).

Two questions...

1) the buzzing noise started after I had vacuumed the inside of the box... I assume that I removed dust asymetrically from the CPU fan blades and that they got out of balance and that caused the fan failure and subsequent message... for future reference, what is the correct way to clean the dust from high speed fan blades?

2) as noted, my build is old... AMD Athelon 64 3200+ Venice CPU on a Asus A8N5X Socket 939 MB... can I still get a new CPU fan for this setup?

Thanks, John