Stock Dell Optiplex 745 memory timings
I mainly do MSoffice work,audio (guitar,keyboard) recording,dvd ripping/encoding/burning
run one Virtual Box VM,light gaming (BIoshock 2,Crysis warhead,Left 4 Dead 2 main games)
recording streaming Netflix and Comcast Xfinity,light Photoshop
I am running Win7 Ultimate 32 but I can switch to Win7 64 if it is worth it do so.

 
FSB- 1066mhz
current ram - 533hz 4 x 512mb (CL2.5 I think)
Still shopping for ram
Probably going to get Kingston Value RAM or Crucial low end
just started looking
I saw Crucial DDR2 800 2 x 2gb @ $70
Also I have four slots
2 x 2gb or 4 x 1gb which is better or does it matter
 
Just take the Cl number and multiply it by 3.75 for the 533 sticks and 2.5 for the 800 sticks to find out which will perform better. the lower total you get will be the better ones to get

Well I did the BSEL pin mod to my E4300 1.8ghz 800mhz to 2.4ghz 1066 mhz
So I figure the memory bandwith increase by going rom 533mhz to DDR2 800 is close to double
from some of the tech articles I have read.

I just reread spec sheet from Dell
and i can only use 1gb DDR2 800 sticks
so it will have to be 4 x 1gb setup