That's more of a guideline. Old software (even 32bit software) tends to write stuff to the directory it's running in. If an application tries to write a file to program files and it doesn't have permission then windows will pretend that it does by creating shadow files. Getting your head around different files appearing depending on who you login in as can get tricky. But not everything does it and if you run with UAC disabled then it won't be a problem (I always have UAC enabled though and recommend it).