C:\Documents and Settings\Spazz\Application Data\Mozilla\Firefox\Profiles\(some profile)
bookmarks.htm and bookmarks.bak are thet wo that have all the bookmark information.
so if you're looking to back them up, just copy those two files, then when reinstalling FF, reinsert those two files in that folder, may be a different profile name though
if you're looking to edit the bookmarks, you have to open FF, go to bookmarks at the top and then click manage bookmarks