Like OGELTHORPE said, you can upgrade to OS X Mavericks without any issue. Make a backup of your files with Time Machine and check that your applications are compatible > http://www.roaringapps.com
However, there's a problem with Windows versions, because Apple only supports a 32-bit Windows 7 version on your Mac, even if your MacBook hardware supports both 64-bit Windows 7 and 8 versions. Anyway, if you install a 64-bit version, your hardware will not work correctly, as there are no drivers for your Mac. You can check that here > http://support.apple.com/kb/HT5634?viewlocale=en_US&locale=en_US