AHCI for ASUS M2N68-AM PLUS

[supercalm]

Hello everyone,

I have an old pc and i got a SSD sandisk 128g the read/write speeds is not that good well better then HDD but still low. In the first copy was pretty nice even with no AHCI
but now i dont know what realy happend and write speed is max of 50-80...
My Motherboard is ASUS M2N68-AM PLUS AM3/AM2+/AM2 NVIDIA Geforce 7025/nForce 630a Micro ATX AMD
I heard something about ACHI, TRIMS, etc, Well in Bios i can not find AHCI i have 3 options on IDE Configuration and that is
1)IDE Controllers
2)Serial -ATA Divices
3) nVidia Raid Function
I am runing Windows 7 x64
Can you please help me and tell me what can i do? Thank you