mancshell

Hi There i have had a horrible issue with my hp pc where its becoming unresponsive every so often (could be 5 mins or 10 etc) and after 2 resets its still not resolved which i was hoping it would be, i even had a issue where my harddrive was telling me it was full, problem after problem which i dont seem to be getting anywhere with getting it resolved , so after 1 week of pulling my hair out i decided to pull the plug my hp pc and plugged a spare compaq pc in that i purchased second hand on ebay which lukily i have had no problems with this one, the only thing is my hp pc has a nividia geaforce 160 graphics card and the replaced compag one has a crap graphics card like a nividia corporation display only device, which no good to play thesims4 which i loved playing on my hp one,, so my hp one is great compared to the other one, also the compaq pc has only 300gb of storage so i would like to put a new harddrive in it, which i can purchase asap, the harddrive in the hp one is only 500gb too, (my pc was purchased in 2009) they both have 4gb of memory too But My Question Is? Could i put my memory stick from my old one to the new one to add more memory and my old nividia geaforce grphics into the new one as well, i have recently installed a new power supply in my hp pc as that failed recently but th compaq power supply is working fine any advice anyone can give i would be so happy because the problems i have had lately its driving me round the bend, i would like to get a new pc but i want to see if ican do something with these until then, thanks for your time michelle