If you have not sure about NT4/XP, but with my windows 2000 there is a telnet service that you can enable and then you can use your windows accounts to access the machine and get a remote command terminal. It is installed by default I believe, best bet would be to search MS knowledgebase or if you do a search in the XP help on your computer, it will search the KB also.
To get you started, here is a HOWTO on enabling telnet server in windows 2000.
HOWTO @ MS KB