Yes, as mentioned windows vista is a little bit slower than windows 7. This includes web browsing by the way. I recommend not spending money on buying a brand new OS, as the speed shouldn't increase all that much, but it is up to you in the end. I gave you a link
to things you can do to increase performance, and if you use the lightweight microsoft security essentials (free and recommended by many) instead of another AV (unless paid for), than it should be just dandy. You can disable some automated things from running, like clearing the startup folder (or startup items in msconfig through search bar), or programs that like to create events where they scan your computer on their own time (windows update, your antivirus, and defrag times can be changed or their schedules deleted so that you manually control when you scan, etc).
You can also remove any program in control panel (try not to uninstall windows updates in there) that you know you don't need, want, or use that may increase overall speed, either slightly or dramatically depending upon the program and how ever many extra such programs you remove