No programs that write to 'C:' or 'C:\Windows' would be installed by me on my own machine or on the company networks I have worked on. No programmer on Unix or Windows (in this day and age) should assume that it can write anywhere but the user's home directory. From a security model perspective Unix and Windows NT have the same level of security. Where they differ in security is that Windows tends to have so much more code exposed to potential attackers compared to most Unix systems.
Hoping that my former employer (and certainly his customer) doesn't read this, but I once wrote a windows application that required to write to C:\ :-). And yes, it really got installed by quite a big company.
It was before the eyeopening experience of finding api calls to retrieve the windows temporary directory :-).
Robert