Machine Debug Manager is if you use your machine for debugging, see link
http://www.neuber.com/taskmanager/process/mdm.exe.html
Commit charge is the "maximum potential pagefile usage" this includes virtual memory so will be your real memory (1 gig) plus whatever it needs from your virtual memory setting. Windows will use whatever it needs so this figure will change.
I have Mcafee anti virus and this also takes up a lot of memory. Something we have to live with.