PC Dead!!

The charity I work for had another PC donated approx 4 weeks ago. It is AMD Athlon XP 2000+ 1.67 GHz, 512MB RAM, 40GB Hard Drive, 64MB Graphics, CD/DVD x52. Untill Yesterday, it worked A1 OK. However, it was on the floor awaiting a desk. When moving it onto desk it stopped working. Absolutely dead – no sign of life atall – even the fan does not try to move. Fuse is OK – power lead works on other machines. Checked all connections and none loose. What can of happened? (The moniter is connected to same power supply and power is delivered to that)