Mouse and Keyboard Have Stopped Working After Disc Cleanup/Update

All,

Background: A few days ago I decided to try to clean up my Dell Studio XPS 7100 a bit by going through and deleting files using the Disc cleanup. I selected all categories listed (to my detriment as it apparently included my previous Restore Points) and also did a little disc de-fragmenting. After all was said and done, my computer decided to do some Windows updates as I shut it down for the night before it completely turned off.

The Problem: The next day I booted up, the mouse (Microsoft IntelliMouse Optical) light on the bottom turned on when the BIOS was up and then shut off when Windows began loading (normal) but did not turn back on again when it came to my login/password screen (not normal). Also, my keyboard (factory Dell) was non-functional. Both are USB. I had to do a hard reset (held the button down for 5 seconds) and tried it again, but to no avail.

What I tried:

1. First I attempted to boot in "Safe Mode" but this didn't change anything. Still, both the keyboard and mouse did not respond.
2. I attempted plugging both peripherals into different USB ports, but to no avail. Every time my computer would turn on, the light on my mouse turned on, and then shut off as Windows loaded up and would no longer respond.
3. I tried using a different mouse (only have one keyboard) but it also didn't register.
4. I tried the Restore to "Last Known Operating" status (or something like that) from the BIOS, it only listed the previous day's Windows Updates and no other previous restore points (because I apparently deleted them during my spring cleaning). I still did it, but with the same results, no mouse or keyboard.
5. Finally, I tired the "Disable driver signature enforcement". SUCCESS! Both peripherals worked perfectly and I was able to log into Windows. The first thing I did was load up the Device Manager and checked to see if there were any exclamation marks or warning by my USB devices. Nothing. I uninstalled and reinstalled all the drivers (uninstalled them and Windows instantly reinstalled them), rebooted, and again, no dice without using the "Disable driver signature enforcement".
6. I unchecked the "Allow the computer to turn of this device" settings under the Power Management tab under "Properties" of all of the USB Hubs and what-not. Again, no dice upon boot up.
7. I did a lot of Googling and found that apparently the SP1 updates are notorious for causing this sort of problem, but when I go to "Uninstall Updates" the last update listed is from December 12th, not January 7th (when it did the updates during shutdown). Since I deleted ALL of the data during the Disc Cleanup (blindly checking away those happy little boxes) I cannot remove SP1, or so I found out today.

What I need: Any advice, suggestions, solutions to this conundrum. I'm assuming this is a driver issue as so long as I choose "Disable driver signature enforcement" every time I boot up by hitting F8 during log in it works; however, this obviously isn't ideal and is just a poor band-aid for the situation. I don't have a Windows 7 installation CD since when I ordered my computer I didn't ask for one (another mistake) but I do have a key registry via the sticker that's on the tower (not sure if that'd help). I'd rather not have to lose everything I currently have though program-wise as finding a lot of those cds would be difficult/impossible. Thanks in advance!

Update: Found that the driver hidclass.sys is not digitally signed and seems to be the root of all of my problems. Not sure why it's not digitally signed as it's downloaded directly from Microsoft, but that's neither here nor there. Is there any way to get it "signed" or a place to download a new, signed version?

I would be curious to know what the original poster did to fix the problem.

Like him, I performed a Windows Disk Cleanup too, and did not select delete all past Save Points for the OS.

However, all the save points are deleted, and the USB devices will not register in the Device Manager. The error states that windows cannot verify the digital signature for the drivers. Luckily my inbuilt keyboard and touch pad are working, but no other USB devices will load.