MS security essentials upgrade error 0x80070645

[cbrescia]

Maybe many of you are using MS Security Essentials or just are unaware that automatic update installs it.
If you have to upgrade it and find a message "0x80070645 error cannot install" and drives you crazy for 2 days until thinking to change the Antivirus because online "MS Fix it" does not work at all, and nothing you read in forums works: here is what to do
Eliminate registry key :
for Windows 7
HKEY_CLASSES_ROOT > Installer > UpgradeCodes >26D13F39948E1D546B0106B5539504D9
for Windows XP
HKEY_CLASSES_ROOT > Installer > UpgradeCodes > 1F69ACF0D1CF2B7418F292F0E05EC20B
Where´s the catch? I have XP and I had to eliminate the first key!
I think it is a bug of the first version installers.
Regards

[SFSxOI]

There should be no need to remove the registry key, although that may very well fix the viewable error message by eliminating the message showing it doesn't fix the actual problem. Besides, the registry key is normal to have and exists on every Windows system MSE is sucessfully installed on and has not caused a problem on thousands of those systems unless there was a botched install or something happened during the install or the version used or upgraded over was a very old version, and the key by its self should pose no issues. This points to a faulty install or trying to upgrade over a very early version or over a beta version or in some cases a failed full uninstall for some previous versions when an upgrade was perfomed by some newer versions (happened about six months ago for some systems). The fix is to download the newest version manually and not upgrade, instead - download the latest version if you need it - remove existing installed (even if it is the latest version) - reboot - install the latest version fresh and clean - reboot - and the issue is fixed, then you should be OK for any future upgrades from there. The registry key should remain intact, its (partially) used for any furture upgrades so if its missing there may come a time when you need that key to be there to allow an upgrade to happen (although, a future version upgraded probably would not use the registry key anyway and simply uninstall exisiting and install a new version like just recently happend in the last few days). Usually you see something like this for MSE when the user has declined or not stayed current with actually installing updates via windows update, or they haven't checked in a while and ignored the optional updates.

[GWarner]

I tried MSE and it is a nice program, but on XP it would never auto update, I had to manually run the update periodically. I could not find a solution and a friend reported the same problem with MSE also only on XP, he said the auto update worked fine on Windows 7. Figuring that it was some incompatability bug, I went back to Avast Home edition.

[IdeasVacuum]

Auto-updates just fine on my XP, but a manual update isn't exactly difficult

[MachineCode]

MSE is just too damn slow. If I open my "Downloads" folder with it, which has just 140 files, MSE won't actually display the files or let me do anything in the folder for about 30 seconds. So I uninstalled it and use Avira Antivir, which lets me access the files about a second after opening the folder. Much better.

[GWarner]

but a manual update isn't exactly difficult

No it's not, but that's not the point.

[skywalk]

MSE is just too damn slow. If I open my "Downloads" folder with it, which has just 140 files, MSE won't actually display the files or let me do anything in the folder for about 30 seconds. So I uninstalled it and use Avira Antivir, which lets me access the files about a second after opening the folder. Much better.

It's not MSE. Windows 7 Explorer has a crappy default setting you can change and your folder with load immediately.
Change each parent folder that exhibits delays.

; Windows Explorer Speedup Folder Listings:
; Organize - Properties - Customize -
; Optimize this folder for: General Items
; [x] Also apply this template to all subfolders

[MachineCode]

If I disable realtime scanning in MSE, the folder opens immediately. Enable it, and it takes 30 seconds. Tried it several times and it's always the same result. There's plenty of Google hits from people posting the same problem.

[skywalk]

I also have realtime scanning and MSE and slow loading of folders.
After making the change I posted, everything is back to normal.