Solar Power for Computer Build
Skip it, seriously. I don't know what your motivation for this is, but you need to learn just a wee tad more before you bite it off. 

If it's (sounds like not) a remote-off-grid solar powered computer, you start with making it efficient, and then then address the power supply (probably not a wall-plug-in-type), days of running without sun, batteries, charge controllers, etc...

If you are on-grid but have vague greenish feelings that somehow have not impacted your choice of power supply/motherboard, just set up a small (or large) grid-tie system and plug the computer into the grid. That will be adequately complicated for you to start learning about.