PEiD (short for PE iDentifier) is a well-known professional packer/cryptor/compiler detecting tool. It's so powerful that it can detect the types/signatures of almost any PE file packing tools (at present, the number has been more than 600 kinds). In addition to the official version, AppNee also provides you its full-plugin version, which can be treated as the most perfect one version (contains 60+ plugins and necessary runtime library files: mfc70.dll, msvcr70.dll, rtl70.bpl, vcl70.bpl) on the Internet at present. I do believe reverse engineers or software cracking/unpacking enthusiasts must like it very much.

For beginners using Windows who are interested in the C/C++ language (anyway, you need to compile your C/C++ programs) or Linux embedded system development, the big headache is switching back and forth between Windows & Linux. Even you have to continuously reboot system in order to achieve the purpose, very troublesome. Cygwin just solved this problem.