Virtual memory is used to assist you ram. It uses the hard drive to store information that is too large for your ram to handle, or it adds more 'virtual ram' to make up for the lack of ram on your system.
When you convert the cd to MP3 it uses a lot of space, it looks like your virtual memory is set too low.
If you use a memory manager like Cacheman it will increase the size of your virtual memory for you. click here There are different options to set, choose the one for your application.