This doesn't mean that you are at risk. Anti-virus detects that your computer has remote control / access tools installed. Sometimes remote control software is being installed without permission from PC's owner. In such cases this is barely legal installation - it may be used to access this computer for spying it's user.
But since you are the one who installed RAdmin onto your PC and surely know that RAdmin is running on your computer, everything's OK. Just be sure to use RAdmin's authorization methods - RAdmin password, NT Security and IP Filter - and no unauthorized person would be able to connect to your computer.
There are three ways to forbid antiviral software deleting Radmin Server:
1. Change default action for "potentially unwanted programs" from "delete" to "inform" or "ask user".
2. Disable "scan for potentially unwanted programs/riskware" option within your anti-virus software.
3. Set anti-virus to ignore "r_server.exe", "admdll.dll", "raddrv.dll" and "radmin.exe" files and activity on RAdmin's port.
Another solution is upgrading to Radmin 2.2. Anti-viral tools don't detect Radmin 2.2 as an unsafe program.