Did you try installing something new recently (hardware or software)? First I'd start with getting rid of that exclamation point in Device Manager. It might need an upgrade, or the driver got corrupted. This sometimes can be fixed by right-clicking the item and choosing uninstall, then restarting your computer where it should reinstall it automatically. Try that.
If not, you can download the drivers from your computer manufacturers website, but for me to help you with that, I'll need some computer specifications. Could you round some of those up for me?
Since in safe mode (which runs with the bare necessities only) it is probably software that is causing your PC to be slow, either updates or programs you installed. I can try to help you figure out what the problems are, but first lets get that driver fixed. Also, go to Control Panel > Security > Updates and check for any. I'm guessing here, but if you have Vista Service Pack 1, sometimes upgrading to SP2 will fix your problems. But then again, it is Vista, and then again it is Microsoft.
Other things can make your computer slow.. malware for one.. but let's take this one at a time.