Well, if you are looking only for Windows 7 then you can use WinDBG debugger which is available for both 32-bit and 64-bit Windows. You have to learn it and just search on Google for WinDBG tutorial/commands and you will get them.
You can also use OllyDbg but I'm not sure it will work on Windows 7 or not, as they have not mention it on their main page and they have just reported that it works like a charm on XP.
You can also take a look on PEBrowse Professional Interactive. Which has two versions
PEBrowseDbg64 Interactive(v3.2) is a 64-bit executable and requires the .NET framework. It will debug Win32/Win64 executables, managed (.NET) and/or native.
PEBrowse Professional Interactive (v9.3.3) is a debugger for Microsoft Windows 2000, Windows XP, Windows 2003, Windows Vista32, and Windows 7.
A very good way if you really miss it set up a virtual machine and use XP Mode in Windows 7 and you can use debug.exe in that way easily. As this question has end with the same solution of VM.