Virtual Memory is exactly that, as I understand it
Windows uses a portion of your hard drive (Drive C
typically) to store temporarily programs and applications
that you are opening or that the computer is using that
would normally be stored in your system memory.
You should not do anything about that message unless you
are an advanced user. The best thing you could do however
would be to upgrade the amount of system memory (which
requires purchasing and installing it) and that would
increase the overall performance of the system.
John