mfehidk.sys is a McAfee service file and can sometime create problems. I was experiencing a BSOD on every boot even in safe-mode. The stop code was 0x0000003B. No matter what I tried, I could not start the system. Scouring the internet didn't prove very helpful so I decided to remove the file and viola, it worked -- breifly. More on that later.
To fix this Blue Screen you must remove the file mfehidk.sys and here is how I did it:
1. Grab your windows 7 install disc (or repair disc). Don't have one? Get it here: download-windows-7-system-recovery-disc
2. Boot from this disc and choose Repair Computer.
3. Select your operating system (usually there is only one to select) and click Next.
4. Click Command Prompt
5. In the command prompt type:
rename d:\windows\system32\drivers\mfehidk.sys d:\windows\system32\drivers\mfehidk.sys.bak
Reboot and it should now allow you to back into windows as usual.
Once back into Windows, you may try to update your McAfee; however, when I did that, I was back to the BSOD and had to repeat the above process. I found the only solution was to uninstall McAfee. Which of course, I couldn't do the normal way -- inside the control panel. Instead, I had to download the McAfee Removal Tool from McAfee here. Before you decide to uninstall your McAfee, you may want to contact their support department to see if they have another solution. I didn't have the time.