Windows 7: BOOTMGR is Missing - Only Sometimes!

I have a strange problem. I read about the BOOTMGR is Missing problem here, and the associated fixes. I get the BOOTMGR is Missing error message, but only sometimes. When I do a control, alt, delete as the error instructs, the computer then boots up just fine usually. All will continue to be well for a while, and during reboot, it will happen again. I've run the Windows 7 rescue disc startup repair option, but it says a problem cannot be found, yet obviously something is going on. I've done the bootrec /FixMbr, bootrec /FixBoot, and bootrec /Rebuildbcd commands at the DOS prompt. On that last command, it told me the number of Windows installations was 0, which obviously isn't right. I'm confused and frustrated by this. Help!

bootrec /FixMbr fixes the MBR but MBR is already fine!
bootrec /FixBoot fixes volume boot sector that loads BOOTMGR and indeed it tries. so looks fine as well.
bootrec /Rebuildbcd rebuilds only non existent boot options in bcd file (as far as I know).

Sequence is: Load MBR->load volume bootrecord->load BOOTMGR->read bcd store (bootmenu)

Problems only on cold boot? Enter BIOS on boot but don't modify anything... just exit bios without updating anything. That makes any difference? Are you experiencing any other strange problems after succesfull boot?

Please post screenshot of disk management

reboot ALWAYS gives that error?
boot ALWAYS give that error?
(CTRL-ALT-DEL fixes it, I know)

No. The error occurs only occasionally on reboot or boot. Another thing: I have three hard drives (not all connected at once) and I only get the error on the one particular hard drive. I have put back my reliable drive back in my PC for now. Later, I'll put the drive back into my PC that gives me the occasional Bootmgr error and post a screenshot of disk management.

check that disk

chkdsk/f/r c:
chkdsk/f/r d:

etc. seagate disk, or western digital?

Western Digital. It's a Caviar Black WD7502AAEX 750 GB. I'll get a screenshot of Disk Management and do the chkdsk tonight, and report back tomorrow. Thanks for the replies, gang.

The chkdsk came back clean. Above is the screenshot from Disk Management.

It looks correct. Run Startup Repair several times to see if it finds anything to fix.

You can also try Rebuild MBR with Partition Wizard Rebuild MBR - Video Help.

If these fail then I would move the System Boot files to C by marking it Active then running Startup Repair - Run 3 Separate Time. This eliminates the possibility that the 100mb System Reserved partition has become corrupted and creates a new System partition refreshing the MBR.

You can also recreate the 100mb System Reserved partition by deleting it using Partition Wizard bootable CD, creating a new Primary Partition there labeled System Reserved, mark it Active then run the three Startup Repairs to write new System boot files to the partition.

You've now done everything possible short of wiping the HD with Diskpart Clean Command which can overwrite problematic boot sector code and solves many problems we have with installs and boot problems.

Be sure to back up a Windows 7 image before any of these operations: Backup Complete Computer - Create an Image Backup
Macrium - Image your system

Thanks. I'll give those ideas a shot, and report back.