The usual reasons for Windows 7 reporting an exe as "Not a valid Win32 application" is for one of the following reasons:
- File is corrupt, bad, or missing.
- File is not designed for your version of Windows.
- File is a virus, worm, or other malware file.
- Hardware incompatibility.
It is most likely not option 2 as it is designed to run on Windows 7 and 8 - I'm running it on both OSes (64 bit)
3 is also unlikely if you've downloaded it from the Teamviewer website. Malware is possible if the code/site had been compromised but unlikely given the volume of users of this product who would have reported something by now.
4 is unlikely unless you have an underlying and undetected hardware issue.
If we look at the reasons for 1 we know your file isn't missing (it's not trying to run a pre-installed application with missing dependencies.) So we are faced with it being corrupt or bad - that is, the file hasn't successfully downloaded completely.
I've just downloaded the same version for Windows (I'm assuming the full version and not the portable version etc.)
Calculating the MD5 hash using WinMD5Sum on it I get the following:
I would recommend running an MD5 sum on the version you've downloaded and compare with the code I've provided above. Unfortunately they don't provide a hash on their website to validate the exe downloaded is valid.