Interrupted Cygwin install changed permissions on C drive

I was installing cygwin on my Windows 7 desktop. I guess I picked a bad mirror site because the download speed was very slow and it wasn't able to give me all the packages I wanted.

I closed the setup in too much haste. I think it was still downloading and not yet installing though. It said that closing it would abort the download and installation, roughly, and I clicked 'okay'.

Now I try to save something onto my C drive, into Program files or whatever, like a text file or anything. It says that I do not have the permissions to do so, asks if I would like to save into my user documents folder, and, in typical Windows fashion, it directs me to ask the administrator. My account is the administrator; I checked both in control panel and in the user select screen at boot.

I restarted the computer. Then I decided to delete all the cygwin files I could find (cygwin folder on C:// and the cygwin download repository) and reran the setup. It successfully completed after I chose a better mirror. I have my terminal window and it works!

But, even after restarting again, I cannot save to the C drive. Interestingly enough, I can save into the cygwin folder, which is in the C drive, but into no where else on the C drive.

I should mention that when I deleted the cygwin folder on the C drive, it was partially full, indicating that I might have stopped the setup initially during the installation phase.

I cannot find any other changes other than this saving permission problem. I can give programs permission to write on the C drive, I can change all Windows settings, etc..

I used system restore to restore my computer to a point before the install, but everything is the same afterward from what I can tell - cygwin still up and c drive still restricted.

What is the course of action to fix this problem?

Thanks!

This is a x-post from techsupportforum.com.

EDIT:
Revo uninstaller does not see the cygwin terminal, so the terminal, it appears, was deleted in the system restore. The cygwin file system seems to be all intact. No other effects seen from system restore.

The cygwin install is not very administrative most of the time, so this is odd. See if you can write files from a session like a console "run as administrator". When I right-click wondows explorer, it says I can "Run as administrator". It sounds like c:\ premissions are damaged, but it may be some related registry thing.