RAM for your Dell is expensive because it has moved to legacy status. It uses DDR RAM which is the most basic available. Sadly your motherboard will not be able to take newer RAM like DDR2 or DDR3 which is far cheaper. I'm using DDR3 which costs about £16 for 2GB and performs at about 4 times the speed of the DDR RAM you are using.
Upgrading with new RAM would be ok, however you are probably only going to extend the computers usability by a year or so.
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