Ok, I need some seriously, wickedly creative ideas on how to fix this. AND...before someone says it...reinstall is NOT an option. I have so many programs on this machine that reinstalling eveything would be a nightmare!! I've have read TONS of forums and website for the past four days with no working solution in sight. The machine simply will not boot up! I get as far as the welcome screen in safe mode and then the error code comes up along with the message "A problem is preventing Windos from accurately checking the license for this computer." I can't do system restore as I had it turned off. I don't have it backed-up anywhere. HELP!! I do have the 'bad' HDD in my other PC rig as a second slave HDD. So I am able to access the harddrive via another working system. Is there some program or creative way I can compare and 'graft' the working registry components from my working machine to the HDD that has the corrupted registry components?? At this point I am at a loss...and extremely frustrated! Maybe it is time to go back being a Mac guy!!!

I see you have XP Pro installed. Ask friends, families or just anyone if you can borrow an XP Pro disc and then do a repair install: http://www.michaelstevenstech.com/X... or http://www.microsoft.com/windowsxp/... also you may try using system restore in the future ;) Hopefully my advice will help you...Please post back with your results....thanks

Can you boot into the BIOS screens? Can you boot into Safe mode? If no BIOS then you have hardware issues for sure. If you can boot into safe mode you might have hardware issues. Further troubleshooting will be required. If you can't even boot into the BIOS screens then strip the machine down to the bare necessities. Processor, graphics, 1 stick RAM, KBoard. No drives, cables, add in cards, periphials. Computer can boot without a HDrive. Post back with results. This could be a RAM issue.

If the suggestions from Responds Number 1 and 2 dont help, then you can try following: If you have another computer with XP loaded, then you can create a BartPE CD. PE stands for Preinstalled Environment. The CD is bootable, it loads a slim Version of XP into a Ram drive and you can access all your drives, floppy, USB devices on the sick PC. It can read all file formats and you can save important files to a USB Memory Stick or a USB Hard drive. It has some tools such as checkdisk and others. To create a BartPE CD you need first download the file Pebuilder.exe about 3.15 MB and install it. Then you are ready to create a BartPE bootable CD. A blanc CD must be in burner before start creating the CD. My BartPE CD has saved me a lot of headaches when repairing friend’s computers. Often time just running checkdisk with repair option have solved problems and the PC,s were booting again. It may work for you; it’s worth to give it a try. Peter

What were you doing before you received the error message? This problem (error code 0x8007007f) frequently occurs after you upgrade a service pack. After you upgrade, there appears to be a corrupted file, a missing file, or a file mismatch. If this is what you did, undo it by booting to Safe Mode & use System Restore to an earlier time. i_XpUser

If I do a 'repair install' will I then have to reinstall all other software? I created a slipstreamed disc - XPPro/SP2 - can I use this to do the repair install? I do have access to the BIOS. I didn't strip down the machine. I took the hard drive out and put it into a working XP computer. But when I try to boot from that drive - the 'bad' drive - that is when the message appears. The OS on the 'bad' drive must be corrupted somehow. Interestly, when I did a check on the 'bad' drive, it tells me that it is a healthy drive and all partitions are healthy. The BartPE sounds like a good option. Is this better than doing a Repair Install?

A repair install does not necessitate software reinstallation. Life is more painless for those who are brainless.