Hi everyone I need some help with this problem that popped up this morning, I started up the computer like normal and this popped up on the screen
*** The File is possibly corrupt. The file header checksum does not match the computer checksum.*** So I did a hard reboot and everything started up ok. Any ideas what this might have been???  Thanks for your help.....Maxwell

Too many Kills on BF3 ?.....just a thought.

Wonky RAM operations can do that, as can a faulty hard drive. It also could ahve been a random hiccup.

Run Chkdsk to check your HDD, and run bootable Memtest86 to test your RAM. jsut birn Memtest86 to a disc or copy to a USB stick, and run teh default tests.

I agree with CHUD; you might have wonky RAM if you've opened your machine recently or perhaps a bit of dust.
Worst case is that your hard drive is starting to fail. I've had it happen to a couple of servers at work and the panic to shift the data off onto another machine makes for sleepness nights.
I suggest a complete backup and then a comprehensive physical disk scan.

Agreed
Backup the disc  
Run the Mem test and Disc checks.

How files get stored is very interesting. When you try and access something it checks the header checksum on the file as compared to where the computer thinks its at and if they don't match it will come up with an error. As everyone has already stated, this could mean Hard Drive (HDD) is going or a hiccup in your RAM. I would definitely back up your data just in case (if you don't already, which you totally should be doing!!! :p).

Indeed. I just had a 500gb Seagate die on me. I've known it's been wacky for months, and i never got around to saving the few files i wanted keep. D'oh. Luckily, 90% of what i had on it was game installs.

At least i have 14 months left on the warranty, so i can afford to procrastinate on that front.