Each time you upgrade, the previous version or build is always removed from Add/Remove. This is how it is with all programs.
In other words, something is seriously messed up with your machine (trust me, I went thru more upgrades than you for v7.0, I have a single entry for MSN Messenger). There's probably some sort of utility you have installed that is backing up and restoring your registry automatically, or you're doing it yourself with system restore. Or something is preventing the upgrade of programs from removing previous version/build info from the registry. You could be infected with a trojan or something, who knows. Or it could be something as simple as downloading and saving, then installing from, an external hard drive that wasn't hooked up the next time you installed, which messes with your TEMP.
Quick fix: open regedit and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall. Locate all three key folders for the previous builds and delete them. An easier way is to search the registry "Find what: 7.0.0xxx" (such as 7.0.0425) and "Look at: Data"...that will find the specific key folders quickly.