Always thought a Mac was too expensive? Think again. The older Mac Pro, which is built of solid aluminium to a tank like quality, is restricted to the older OSX - Mountain Lion (operating system - pre 2007/8). This makes it practically obsolete as nothing will run on the damn thing. BUT, you can fix this with a clever hack so that it will run nearly the LATEST OSX - El Capitan, where everything installs and runs like a dream. You can even buy cheap hard-drives where the hack and El Capitan is already pre-installed for just £20 (I just bought one ). You might have to replace the graphics card as the original graphics card might not be recognised under El Capitan (will still run but not all resolutions will be available). You can check on this by searching for the name of your card along with El Capitan compatibility.
My own 2006 Mac Pro (12 year old machine) flies as it has 2x 3GHZ Xeon Processors - 16GB Ram and a Hybrid 1TB hard drive. I purchased this machine a few years ago for around £250. To upgrade to El Capitan a new graphics card was called for. I settled for the ATI Radeon HD 5000 1028 MB which works a treat - attained off Ebay for around £40 I think it was. The hard drive was also upgraded and such hybrid hard drives are very cheap now - it is silent and very fast (not an essential upgrade as there was already 1TB of hard drive space split between 2 500GB drives, which I now have spare, but one of which holds a cloned image in case of any problems in the future).
Check out the prices of some of these machines below.mac pro 4 core 2x 2006 quad Ebay UK Search