I think you will find that the limiting factor in this laptop is the processor. 2 Gb of RAM is sufficient to run Win 7 even if part of it - the 400 Mb - is reserved for graphics.
I would be more concerned as to why it crashed in the middle of a Powerpoint presentation. Running Powerpoint is not a terribly demanding application, and, as I believe this is an older laptop, I would be concerned about possible overheaating problems. To this end, I suggest you install 'Speccy' which you can get - for free - from :
and run it and see what it says your temperatures are after the computer has been running for a while. As a guide, the processor can safely go up to 65 - 70C, a typical motherboard temperature would be in the range 35 - 45C and hard drives 25 - 40C.
If any of the temperatures look like exceeding these values it is time to get out the vacumn cleaner, the can of compressed air, the soft brush and perhaps a couple of small cross head screwdrivers to get into things like fans ! It is surprising how much muck and dust can accumulate inside a computer after a year or two !
Of course, your temperatures may be entirely nominal - Windows computers can crash at any time for a multitude of reasons, and usually at the most inconvenient and embarassing time.