It means you are low on virtual memory so the Windows operating system will make it bigger the first chance it gets.
You computer will have an amount of what is known as RAM. (Random Access Memory.) These are physical chips on a board plugged into your computers main board. Wherever possible when memory is needed these real chips are used as they are fast and designed for the job.
Since modern PCs run software that uses loads & loads of memory (esp Windows) Windows will predict you needing more and when first set up will have reserved a chunk of your hard disk drive to save stuff and read back. This is known as virtual memory since it will be used the same way as your real memory but will inevitable be slower and so not used unless needed.
The message you got is basically saying that you are running so much stuff that not only are you pushed for real memory to use, the space reserved as virtual memory on your disk drive is also struggling to cope with demand. So Windows intends to reserve more drive space as soon as it can.
Best solution is to install more real memory since for reasons of speed you don't want to be relying on the virtual stuff if you can avoid it.