Power supply for the Hewlett Packard Media Center M370N

[Eschatos]

Dear Lord. After hearing many people suggest that some of the issues with the game might be power supply related, I decided to check if my computer's--which I inherited--power supply matched what the Radeon 9800 (which I haven't had problems iwth prior to this) suggested. Basically, it suggests a 300 watt (or greater!) power supply and the M370N apparently has a 200 watt power supply. On top of this, I've read that the dimensions of the case make upgrading the power supply impossible. However, these same articles have said that upgrading the card was also impossible and its previous owner managed to do that (hence, the Radeon 9800). My main question follows. Is it possible to upgrade the power supply on this machine? Help!!!