|By VRAM I'm guessing you mean the 64 meg dedicated video memory and not virtual memory (which VRAM usually refers to).|
'Dedicated video memory' is exclusively used for video. It's a separate physical installation on your laptop's motherboard. 'Shared memory' is part of the system ram and is carved out of your 4 gig total.
You can usually adjust shared memory in cmos/bios setup but it's unlikely you can change the dedicated video memory. Apparently some of the C660's came with 64 meg and some with 128. You must have one with 64 meg. Even if there were some available empty sockets on the motherboard for more video ram you'd still have to open it up and pull out the motherboard and buy the ram somewhere.
(I mention that because In the old days some motherboards with on-board video had extra sockets where you could bump up the video memory from 1 meg to 2 meg--wow!)
If by VRAM you really do mean virtual memory well here's how to change that:
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