I installed the unstable version, there is no stable version yet for Windows.

To bad.

But now, I'm wondering if there is a way to uninstall it?

Simply running the KDE on Windows installer again and selecting the appropriate option should remove KDE from your computer.

I wish it was that simple. I have win7 64 bits. runing kde4.exe (with admin priv and compat xpsp3) from progra files(x86)/KDE/bin doesn't do anything.
Although I managed to unistall it your explanation was not clear enough for an unexpericed user. It has to do with the package manager.

It worked for me, I guess?

add to delete shortcuts though.