Without knowing what software you are using it's hard to tell exactly, but it will be something like this.
On PC open up your email software, probably outlook or windows mail, find your account section probably tools, account or similar in there change it from pop3 server to IMAP server if that is an option, it should be then change the server address to IMAP.virginmedia.com
SSL should be enabled and port number should be 993
There are numerous guides on virginmedia help pages telling you how to do this,
there is another option where you log into virgin webmail and change the pop settings to not delete emails when downloaded or something like that but you are better off using IMAP on all devices