I newly installed Skyrim and I spent a long time installing mods, including ENB. I started a new game and it played very smoothly. Shortly after, I updated my Creative Sound Blaster Z drivers, and since then Skyrim has lost FPS.

I'm not sure why that happened, but do I have to completely reinstall Skyrim? Is there another way to get my performance back?

Thanks.

Uninstall your Sound drivers and reinstall the factory shipped versions with your install disc.

Next open the start menu and select Run, type msconfig, hit enter, the MSConfig tool will open, select the Startup tab, uncheck the following: "UpdReg" & "CT~Hlp" (where ~ represents either au for Audigy cards, XFI for X-Fi cards, etc.), click Apply then restart your PC.

These are Creative background apps that really serve no functional purpose for you and can cause spikes in CPU usage.