I am using lightroom 4 on Macbook. I am switching to Windows in a week's time. Will I be able to use my registered copy of Lightroom 4 on windows after uninstalling it from my Mac? Please let me know.
Unlike the rest of the Creative Suite, Lightroom is a multi-platform license so you can install with your serial number on both Windows and/or Mac.
No need to uninstall it from your Mac, unless you really want to, since you can activate the software on up to two computers simultaneously.
Just download the Windows version from the Adobe website (since the Mac .dmg file cannot be read by Windows) and install it using your existing serial number.