Error 5: Access Denied suggest that you do not have the proper credentials to logon to the remote machine. Over and above everything else, whatever credentials you are using to attempt the remote connection must have rights to logon locally to the remote machine. In other words, the credentials must be a member of one of the following groups on the remote machine:
However, if the remote machine is running Windows XP, then this behavior could be related to "Simple File Sharing". Windows XP Home & Windows XP Professional installed on a machines as part of a WorkGroup has "Simple File Sharing" (not to be confused with "File & Printer Sharing") enabled by default which offers no NT Challenge/Response Authentication. "Simple File Sharing" also does not allow you to remotely install/remove/start/stop the DMRC Client Agent Service. "Simple File Sharing" cannot be turned off in Windows XP Home, therefore you must manually install the DMRC Client Agent Service on machines running Windows XP Home. Once the DMRC Client Agent Service has been installed, then you should be able to use the "Encrypted (128 bit) Windows Logon authentication method to connect to this machine.
There is also a policy setting in Windows XP that does not allow you to access a remote machine running Windows XP over the network using an account that has a blank password. Therefore, if you are using an Account with a blank password, I would suggest that you create a new account with full Administrator rights and assign it a password. Then use that account when attempting a connection via the Mini Remote Control program.
Information About DameWare Development Software's Compatibility with Windows XP:
How To Manually Install or Remove the Mini Remote Control or NT Utilities Client Agent Services: