Well VirtualAcorn does certain things with the hardware particularly CD Drives so Admin privileges maybe advisable... However if you rarely load anything from an 'Acorn Format' CD then to get round your problem and run VirtualAcorn from a 'Restricted User' Account you need to navigate within Windows to C:\Program Files\VA (or whatever the Virtual Acorn folder is within Program Files anyway) and change the file permissions to 'Everyone' - Full Control. You may have to 'turn off' 'Use Simple File Sharing' in Windows Explorer. For a total solution you could of course read my complete article on this in RISC World (not sure which edition), but it will be on the RISC World DVD I imagine....
http://www.riscworld.co.uk/