Windows Backup .... Cannot create a file when that file already exists. (0x800700B7)

Did you try creating another user in case your current user's profile has become corrupted?

Try running ChkDsk to check your drive for errors. Right-click your Drive icon/ Properties/ Tools/ Error Checking.  Try it first by not checking either box (Read-only mode) to see if it flags any hard drive or file problems.  If it does, start by ticking both boxes, in any further rerun.

Something like the System File Checker might help if you have System Files missing or corrupt.

How to repair the operating system and how to restore the operating system configuration to an earlier point in time in Windows Vista (or 7)

http://support.microsoft.com/kb/936212/#appliesto

How to analyze the log file entries that the Microsoft Windows Resource Checker (SFC.exe) program generates in Windows Vista

http://support.microsoft.com/kb/928228#appliesto

How to use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7

http://support.microsoft.com/kb/929833

After that lot it may be time to think about saving your valuable data and making a fresh start.  What recovery options come with your machine?  Is it the usual OEM stuff or are you lucky enough to have a Retail DVD?

Here is some advanced procedures you can look at if you are happy with it.

These two articles in the RegEdit Help are a good explanation of the process.

To load a hive into the registry

To unload a hive from the registry

How to edit the registry offline using BartPE boot CD

http://windowsxp.mvps.org/peboot.htm

Basically you would attempt to import your registry file into Windows Vista, or 7 system, using another operating system to do it for you.

Thanks for the info, Linney

yes, I get the same error message even in safe mode i.e. the exprted copy of TaskCache on my desktop cannot be imported or merged back into the registry, with the same

'Cannot import C:\Users\XXX\Desktop\TaskCache.reg: Not all data was successfully written to the registry. Some keys are open by the system or other processes.'

error message. The link you provided for vista scheduled tasks explains what all the standard default tasks are for, most of which I've had an error message for, telling me that the task is missing. However, there is no suggestion as to how to go about recreating the tasks. Given the recommended fix, and the fact that I made an export copy of TaskCache, I would have thought there must be a simple way to just put it back into the regisrty. As for security, I have access control turned off & only have one user with administrator rights, so don't think access permission is an issue. All I want to do it put the deleted WindowsBackup folder back into the registry and am not sure why this should be so hard when I have a ready copy of it to use. & that's before I even think about trying to fix the loss of ability to create restore points again . . .

Do you get the same errors if you try it from Safe Mode?

Vista Advanced Boot Options (or 7)

http://techblissonline.com/vista-advanced-boot-options/

Have you looked at your System Restore problem if you create a new user and test with that?  Maybe they'll have better luck than your current user?

See if you can make use of this to create all the missing Tasks?

Description of the scheduled tasks in Windows Vista

http://support.microsoft.com/kb/939039

Use the Vista instructions in this to reset to default the security settings.

This is something to try if your Access Permissions (and other Default Settings) have become corrupted.

How do I restore security settings to the default settings?

http://support.microsoft.com/kb/313222/#appliesto

I tried Della's fix, but it didn't work. Still not able to create a restore point. I've then opened up the task scheduler & have lots and lots of error messages relating to all sorts of scheduled tasks that have now been removed as a result of deleting the WindowsBackup folder from TaskCache\Tree\Microsoft\Windows, per the fix. A lot of these scheduled tasks that no longer work were not set by me, but by the system/software etc etc & I have no idea how to replicate them manually, or even what some of them do

I did export a copy of TaskCache to my desktop before I deleted the WindowsBackup folder, as suggested above, but I cannot find a way of replacing it back in the registry. I have tried doubleclicking it, & also merging it, but keep getting the message -

Cannot import C:\Users\XXX\Desktop\TaskCache.reg: Not all data was successfully written to the registry. Some keys are open by the system or other processes.

Has anyone got any ideas how I can restore these entries to my registry ? I only started this because I can't create any restore points, and my previous restore points have been deleted, so I can't use that as an option. Now I still can't create restore points AND all my scheduled tasks have gone too. Please help !!!