I'm getting a Virtual Memory is Low error message
First off, understand that virtual memory is a part of the computer's hard drive that is set aside and used like RAM by the operating system. When the physical RAM is all used up, the operating system begins to use the virtual memory. When the virtual memory is nearly all used up, the "Virtual Memory is Low" warning message will pop up.
Close open programs
If you have multiple programs open at the same time and they are using up the majority of your RAM and virtual memory, this can cause the warning message to pop up. Fixing this requires you to close one or more of your open programs, to free up virtual memory and physical RAM space.
Close and then re-open programs
The second possible cause is similar to the first, with the major difference being that one specific program is using up most of the available memory. Reasons for this can be that the program uses a large amount of memory, in general, to process a particular function. For example, photo editing, video editing, and CAD drawing programs can use up large amounts of memory at times. It's also possible the program is not functioning correctly, stuck on some process and causing it to use large amounts of memory. Try closing the program and re-opening it to reset it and correct the issue.
Reboot the computer
Rebooting the computer can help close any background programs and restore any memory that hasn't been recovered. Reboot the computer and see if the virtual memory errors continue.
Not enough memory
If your computer is several years old, not having enough memory for software programs to run can cause virtual memory errors. For most computer's today, it is recommended that a computer has at the very minimum 2 GB of memory and a recommended minimum of 4 GB of memory. The more system memory you have, the less virtual memory will be used.
The third possible cause is a bad memory chip. A defective memory chip results in some of the memory being unusable, reducing the amount of memory available overall. In many cases, a blue screen error will occur when a program tries to access the bad part of the memory chip. In other cases, however, the low virtual memory warning message may be all that appears. Replacing the bad memory chip usually resolves the problem.
Bad hard drive
Lastly, a bad hard drive could also cause this warning message to appear. If the section of the hard drive set aside as virtual memory becomes corrupted, the operating system will not be able to use it and can result in virtual memory warning messages. You can try repairing the corrupted sectors on the hard drive (using a hard drive repair utility) or replacing the hard drive to resolve the problem.