Windows 7: MSE gives big problem!! Sysnative

After installed Microsoft Security Essentials, I have got a huge folder in my Windows-folder (abot 3,8 Gbyte), that I can't get rid of again. The name of the folder is Sysnative and there are no attribbutes or date/time on it. I can read it, but that's it. Then I tried the "take ownership.reg" from this forum, and I got permission to delete few of the files, but that was NOT a good idea. Some system-files could not run after this, f.i. cmd.exe could not start (error 0x00000154).
I have now restored back to before I have deleted the files, but how do I get rid of this big folder again? It did not help to uninstall MSE.

Do I really have to clean install Windows 7 again?

I've never had that happen to me. I've been using MSE since its public (then not so public) beta, now I'm using the Ongoing beta builds.

I wouldn't know what to do to get rid of it, its a bit odd it appeared in the first place.

Well, if it is not MSE I really don't know what it might be, and why some Windows systemfiles can't run if I manage to delete about 5 Mbytes of the total. As written no dates, no atribbutes, no owner, I can't take control over the rest (and that does not matter as Windows can't run properly, if something is deleted anyway).

This is Microsoft's explanation of this, but I don't get the meaning of it:
32-bit applications can access the native system directory by substituting %windir%\Sysnative for %windir%\System32. WOW64 recognizes Sysnative as a special alias used to indicate that the file system should not redirect the access. This mechanism is flexible and easy to use, therefore, it is the recommended mechanism to bypass file system redirection. Note that 64-bit applications cannot use the Sysnative alias as it is a virtual directory not a real one.

I don't have time to read that thoroughly sorry.

I believe if you boot into safe mode and log in as admin. You can delete it that way. :S

Wish I could be of more help.

Sounds like it has something to do with making 32bit apps work on a 64bit system. Not really a folder with files but rather a junction point (folder redirection) pointing to a system folder. I would say you should not try to delete it!

File System Redirector (Windows)

I have to ask...what in the world are you doing deleteing files in C:\Windows? Never ever do that without thorough evaluation! Even then do not delete files from the Windows directory! C:\Windows\Sysnative is for 32-bit application to access C:\Windows\System32 on 64-bit editions of Windows otherwise they are redirected to C:\Windows\SysWOW64.

I hope you have a restore point...otherwise...try a repair install then a full reinstall if that doesn't work.

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Look here for information about the sysnative directory.

Selectively suppress Wow64 filesystem redirection on Vista x64 with ‘Sysnative’ Nynaeve

Well, mine Sysnative does not behaive like it is described in your links. I now know why NOT to delete any files in it (systemrestore corrected it), but not for the reasons mentioned. My system32 and my sysWOW64 is now including EXACTLY the same files, versions and dates, but I don't know if this are the 32bit or the 64bit versions, and Sysnative now holds the other version, so I have 3 folders where should only be 2. And yes, _my_ version of sysnative is a real folder, taking up hdd-space, and so are both system32 and sysWOW64.
Seems like I will have to do a clean install again this weekend, but I'm annoyed about not knowing where it went wrong. I will buy a program to make systemdisc-images (ghost or .. ??), and then test from scrap on again.
Deleting a hole system folder is way over my head!

Open up a command promp, travel to C:\Windows then issue DIR. Junctions will be flagged with <JUNCTION> instead of <DIR>.