Bios Mods -The Best BIOS Update and Modification Source

My question is simple to keep the Sempron 145 on my father pc or to put the Athlon x2 4000+ that is atm sitting in a box (I upgraded from Athlon x2 4000+ to Athlon II x4 640).

tomshardware didn't helped me at all cause they don't have a Hierarchy that include sempron cpus (here: http://www.tomshardware.co.uk/best-cpu-o...087-6.html i see only athlons and phenomens, looking on net I didn't saw some relevant comparisons: in some tests x2 4000+ is better then 145 in others 145 is better then x2 4000+ ).
He uses the pc mainly for web browsing and play some online games (like guild wars ( with me so i can be rich in guild wars lol, I steal his money in guild wars )).
My father pc configuration is:
MB: ASrock N61P-S (with the semiofficial bios that added support for sempron 145 (semiofficial cause the asrock support sent it to me in one e-mail but there is no official release on their site that support it))
RAM: 2 x 1GB DDR2
GPU: ATI HD4350 512 MB
Sound: SB Live 5.1

The Sempron 145 fail to unlock (at least on the mb that i have).

That MoBo doesn't support unlocking cores unfortunately.
I'd stick 4000+ in and overclock it. It's frequency is 2.1GHz, right? They can easily go to 3.0 and maybe higher. So set they memory from DDR2-800 to 533 and then raise HT frequency to 300Mhz by increments of 10MHz. When you get to your goal, run multiple stress tests. If necessary, raise the voltage a bit (look after cooling the CPU though).

Online games get use of the second core so a Sempron won't be the best.

Yes the 4000+ frequency is 2.1Ghz (it's a brisbane).

I tryed to unlock the Sempron 145 with an asrock K10N78D it was always failing (without changing voltages and limit memory freq was failing to boot any os, both linux and windows were hanging at boot, only by raising vcore and setting ddr2 533 windows was booting, ubuntu 10.04 was hanging from time to time, but it was giving errors in prime) so i assumed that something is wrong with the second core (or maybe the nvidia unlocking is not that well implemented).

Hopefully n61p-s is better then asus m2n at overclocking. At least the M2N i have is faling to boot with fsb higher then 217 (doesn't matter what i do with the other bios settings: ddr2 freq, ht)(had same problem with the several bios versions: 803, 808 (this one looks to be bugged it reports wrong cpu freq and wrong cpu temp), 902).

I've pushed the N61P-S to about 315-320HT. 300MHz is no sweat with the right memory settings.