You can run 32-bit software. Athlon 64's can run both 32 and 64-bit software.
Even if you have a 64-bit operating system, you can still run 32 bit software. Just not 16-bit legacy DOS programs.
If everything (software and hardware) are optimized for 64-bit, it will be faster. Get loads of memory too. Especially in intensive programs where lots of calculations are used, you will see a big increase in speed.
ok, so you said you oc... how'd you do it in bios? what kind of bois do you have? My freakin bios sux and I'm wondering if you have the same one as me.... yeah... thanks
Yuck... the pent. d = yuck. The sempron is old... the athalon 64 3400+ = yes, get that. Make sure it's socket 939 to0, so you can upgrade to dual core's later on. Or just an X2 4200+ and save yourself the trouble.
Socket 754 doesn't support as high as bandwidth either....
Anyway, @ $Thread_Title :
Yes, the 3500+ is a good solid CPU thats at 2.2GHz and can be OCed although I wouldn't recommend it with stock cooling, if you get arctic silver 5 thermal paste and a nice zalman cooler...you could OC it up!