HELP--Slow performance under Directx 9.0c(last) or MS Visual C++

Hi, i would like to know if any of you can tell, if had experiencied slow dow after installing the latest updates for directx 9.0c(april 06+) and /or microsoft visual C++, and maybeb ageia software. Every time i had to format my computer i install my gamme and these brings theses software and updates, after doing so especially with GRAW, GOTHIC 3, and OBLIVION, my pc begins to drop like a 20-25% in perfomance. I noticed long ago, since i always love to play most wanted, after installing some of these games, most wanted doesnt run as before, same happens with battlefield 2, that i even use the mod for 64 players on map, and my computer run it perfect. I fixed this problem by not installing these updates.It was hard for me to know these because once installed the computer remains the same even if you uninstall these softwares, so i had to reformat it again and be in alert to not install those upsates. I ask for an expert on this matter to investigate what is happening, cause for me i believe is evill from giant software company. Thanks and i hope this works for someone.

---MY PC SPECS----
INTEL p4 3.06 HT
ATI 9800pro 128mb
2GB memory
160GB Hard disk 8mb buffer, SATA
MSI 865PE neo2-v/ PC CHIPS T12 v1.0( it happens in both motherboards)