You don't have two operating systems. If you did, you'd be presented with a menu every boot, asking you which one you wanted to start. And even that isn't always a sign.
Vista Ultimate can upgrade any "lower" version in place. At their core, all versions of Vista (and 7) are the same. Different features are just switched on or off depending on which version you have. Ultimate basically switches them all on.
As to why your system is suddenly running slowly. My first guess would be malware, but I'd suggest making a new topic with a title more related to that issue. Improves the odds of someone stopping by to take a look.
I need to know how I can find out if I have two Operating Systems on my computer. It came with Vista Home Premium, and I won Vista Ultimate (not an upgrade) at an event. A couple years ago I installed Ultimate, but I don't remember if I uninstalled the other one. My computer sometimes runs very slowly and now I'm wondering if I did it incorrectly. I really don't remember what I did. I can tell you when I start the computer it does NOT ask me which OS to use as I've read on some threads. Thanks.