I'd like to add to this thread am an owner of a Cooler Master Cavalier 2. It is a slimline desktop case that I love. It is old and discontinued, and upon further research, the PSUs in these things die and are proprietary. I've had to replace the PSU twice so far, and just recently blew the 3rd one. The dimensions of the original 300/350 PSU are 120mm X 86mm X 155mm. There is little info around on a decent PSU replacement for this awesome case as I have been rooting around for a while looking for something that is compatible.
If you are like me, then this post is for you as I have stumbled upon some great info for Cooler Master Cavalier owners looking to replace their PSUs. Apparently a company called Lotus Electronics Design & Manufacturing Co., made the Cooler Master Cavalier cases; here is a link to their slimline desktops (which are identical to the Cavaliers) http://www.lotustronics.com/desktop.htm Check out the Power supplies and note the dimensions. Ok, also hidden from the website is a more-powerful PSU. I found a reseller of the Lotus Electronics stuff at UserEasy. Here is a link to a compatible 460W PSU for the Cavaliers and the slimline cases that Lotus still currently manufactures: http://www.usereasy.com/product_11839.html
I called Lotus and confirmed that they were the original manufacturer of the Cooler Master Cavalier Slimline cases and the supplier of the Macron Power MPT-350D & MPT-300D PSUs. They confirmed UserEasy as a reseller and told me that the Lotustronics ATX-460W Power Supply is compatible with the cavaliers. So those of you rooting around looking for a PSU replacement for your cavalier, I hope you read this post.... Incidentally, I love the case so much that I ordered two of the 460W PSUs in case I blow the next PSU. I don't want to go on this wild goose chase again.