I wanted just to tell you that in all Windows there is a debugger for DOS.
Just write "debug" (without "") in prompt and u'll have the simplest debugger u've ever seen
. You can do a lot of things with it:
Write in memory, See the content in a particular memory address, Search for specific bytes sequence or string, Load a program in memory and Debug it, etc...... (It works also as a disassembler!!)
I think a lot of people dont know about this useful tool, hope this advise could be useful
Unfortunately i've only an italian site where there is a great howto for this tool, so if u're interested just search around the net for others.