|On lan or wan?|
Does user have password? Needs one.
Check that the port has not been changed. If on AD be sure
user has checked rdp.
Scan network and view packets maybe to see how far along it
Ping is useless.
Go to start, run, the type in cmd, once in the command
prompt type services.msc, on both machines.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10