There's no need to split the hard disk into partitions. If you already did, then check which partition is running out of disk space, but the error message probably indicates that you're running out of system memory. Have you checked what Task Manager reports?
How much physical memory do you have installed, and how much virual memory has window dedicated? Low memory is the normal reason for this error. How much free space do you have on HDD?
Most laptops ship with just a single partition - The "C" drive. I prefer a "C" (I normally use a 200 gig partitipon size) for operating system and programs and the remainder for a "D" drive for all the files/data that I generate. On big advantage to this is in terms of imaging the "C" drive and Backing up Your generated data.
With windows 7 this is relatively easy. Just go into Disk management and "Shrink" your "C" drive. If Win 7 will NOT let you shrink it, it is do to the hiberation dot sys file that windows sticks at the end of the disk. All that is need is to disable hiberanation, reboot and run disk cleanup.