damn, still on the google lock screen.
You are slowly killing me. Md5 is for verifying your downloads. What you are most likely encountering is a corrupt download.
If you download roms directly to your phone, try this: MD5 Checker.
If you download your roms to your computer, then transfer them to your phone, try this: MD5 Checker.
You can usually find the md5 hash code in the OP of the rom you are downloading. The developer will ALWAYS provide one. Copy this code into the MD5 Checker, then load up your rom and let it verify. If it matches, your good to go, flash away. If it doesn't match, you have a corrupt download, re-download.