NEED HELP!!!

Hi I have a problem with my computer it had been getting lots of bsods
lately such as alcxmntr.exe and nv4 disp.dll error i managed fix the nvidia
one by reisntalling my grahpics card. However now after 1 month of bsod
i been getting more werid bsods which i dont remeber.
Here are my com specs its been 7 yrs lol
Compaq Presario S4150AP
Intel 4 2.4ghz
1GB Kingston DDR RAM (used to hv 512mb one of the 256 burned, i used to use 1256mb ram)
but after 4 months since i changed the grahpics card
to a 7300GT 512MB i managed run 1256mb ram and play most games at med
grahpics
my PSU i tihnk is 240W
and motherboard AGP1.0 N1996 MSI DDR
i was thinking the problem might be forcing the grahpics card to work
considering it required 300W and 2.0AGP Motherboard
i am going get a new i7 soon but i still want fix this com
so i can give to my mum to use, we always fight over the com when she
needs to use it lol.
so to what i read up on i think it might be the
1. PSU not enough
2. AGP 1.0 MB nid change to AGP 2.0 MB
3. my RAM is old too i thought of changing to DDR2 RAM
4. LOTS dustbunnies nv clean my com for yrs
5. what u think which is the one affecting the most that MUST be changed??