Make sure your Java runtime and Adobe flashplayer are installed; available from their websites.
Check the event log by right clicking computer>manage then browse to Administrative events. Resolve Critical issues immed. Google persistent errors to see what they are, or ask here.
In Device manager look for any exclamation marks signfiying problem drivers
type CMD in startbox, right click Run as Adminstrator and run "sfc /scannow" without quotes. It will verify every OS file to see they are intact and uncorrupted, the next best thing to a reinstall.
Finally, if I had performance issues not sussed out in events log, or other advanced performance tests you can click through to from Computer>Properties page, I would run my Windows 7 installer from desktop and do a repair install which saves everything in place but reinstalls the OS under it.