I would run the pressure on the regulator down to aroung 30-40 lbs to avoid dislodging your components and make sure to drain the compressor prior to using it on electrical components to remove the excess water. You should have no problems
yeah dont spray parts dircetly, (the case is cool but not your mobo) use a pencil or something to stop the fans from busting, and you may still need to wipe the sides of the case off with a damp cloth if there is still dust on it
Dekar12 & MajorDomo basicaly said it all i was just adding my $0.02 USD (and giving you another vote to go for it man)
when i have a lan at my house, the computers go into the garage to be cleaned b4 they come into the house (like a little quarenteen)