hunter315 :
What are the timings and what do you do with your system? If you are running a 32 bit OS then you wont even be able to use a full 4GB so the 8GB definitely isnt worth it
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.