I am currently building a new pc for the first time. I am gonna buy an ssd samsung 830 128gb and was wondering if instead of buying a new hdd for storage, if i could just move my old one from my old computer and use it in the new build.
As long as the new motherboard has a controller to support the old drive than it will work. So, if your old drive is an IDE drive, the new board will require an IDE controller.
You could use the bios to switch which drive to boot from. The problem is that Vista will have all the drivers installed for your old motherboard and it will most likely crash or not boot on a new motherboard. You could try a reapir install of vista once it's in the new machine, but if you really need vista, I'd do a clean install of it.
If you plan on dual booting and doing a clean install of vista, you need to install the OS's in order from oldest to newest so you would need to install vista first, then Win 7. Honestly though, I'd stick with 7 and get rid of vista.