A virtual directory afaik is a folder in your domain for example that points somewhere on the servers hard disk. Hence being called Virtual I think.
You need to have access to the server.
Is it your webserver?
Start -> Settings -> Control Panel -> Administrative Tools > Internet Services Manager
I think that's it roughly off my head.
Once you have loaded ISM, locate the website on the list of sites on the left. Most servers will set the name up as the domain name so look for yourfriendsdomain.com and RIGHT CLICK on it. Move down to NEW then click VIRTUAL DIRECTORY.
I may be wrong here but I am pretty sure that isi what you are asking?
Someone feel free to correct me if so.
EDIT: To run ASP you shouldn't need to setup any virtual directories as it is setup as standard with IIS.