I recently downloaded iTunes 10.5 on my Windows 7 computer and ever since then the iTunes store will not open
There have been a lot of problems like that lately. If you want to take a stab at troubleshooting, see this document: iTunes 10.5 for Windows: May see performance issues and blank iTunes Store
Only concern is, if I delete iTunes will I have to re-load all my media files that I loaded on off of cds, also store purchases?
Of course not. The files will still be on your computer. However, the fact that you are concerned indicates that you may not have a suitable backup. Get an external hard drive and make a backup of your valuable content.