Vista is legacy (
mbr) and 10 is the current (
efi) system... they don't get on.
The guide posted above is very good but it is only a guide... yes give it a go but have you got a different computer to use, for when this one falls over?
1. A fresh install is the best i.e. remove Vista and just have 10... on a back up computer, not your main or only one.
2. a multi-boot is almost as stable and doesn't remove the old Vista... You do this on a system that has more than one hdd.
Again, it's your system--- good luck.