I agree with the above. Yes you can use RADMIN or PCA, but you will also need to know the port number if it is not the default. Plus, if he is running anitspyware/virus, internet security, something would would pop up with "program trying to gain accss." However, as far as I know because I do use them myself, the other PC would also have to have the programs installed for it to work. Windows Remote Desktop Connection, or on W2k Terminal Services, as long as the other PC has it active, you could gain access.
However, since you really did not described "bother" I am assuming he is able to access your PC. If this is the case and you have a cable connection, ask your providers to change your IP. DSL will change it every time you turn off your modem for 5m. If you do know his IP for sure, say he is on a static IP from a cable provider, use a program like ZoneAlarm or Norton Internet Security (maybe Windows Firewall does it) and block his IP from gaining access. Set your PC up to block any unauthorized access into your home PC. If it becomes too much of a hassle from him, you have log entries (denied access or grainted) of his IP which can be traced to him if you did report it to his Internet provider (because they know which IPs belong to them). You can bring the logs to the police if you trust them.
Hope something in here helps.