If they were both booting for a month and now you can't boot windows, something or someone changed something in the bootloader. Without more details there is little that anyone can suggest, we can guess though. use google or whatever search engine you want to find the bootinfoscript, read the instructions and download it on Red Hat and run it. It will output a results.txt file which you can post here to get help.
Here's the link to their site:
http://sourceforge.net/projects/bootinfoscript/
