Whenever I install any antivirus on my PC and try to run any executable file or to launch any other program, here comes an extremely annoying message that never goes off and reads as follows,"Windows Can't access the specified file,device or file, You may not have the appropriate permission".
Whereas I run the administrator account and am running the windows xp and antivirus I've installed is the avg or any other antivirus it will get the same result.
If someone have the solution to the problem, let me know the solution please.

Try disabling all anti-virus or try installing in safe mode.

Disabling all the antivirus will render my PC vulnerable to security threats and I can't understand the safe mode installation please let me know what does it mean.

Disconnect the PC from the Internet, disable the A/V, reboot install your ned software then re-enable the A/V and reconnect to the Net.