This isn't a fix for you, but I have a similar problem (although not as bad).  I also downloaded the driver update installation program from the Dell support website for the PM55 Express Chipset Family, and it didnt update anything.  This is the same result for every driver update installation program I've downloaded from Dell.  It's like the installation program isn't doing anything at all.... it's weird.

My post (with no answers yet) can be found here: http://en.community.dell.com/forums/t/19329299.aspx

I assume that you first used the installation discs that came with your system?  You should do that first before trying the downloaded stuff (imo, but it might not matter).  Also, you can try uninstalling the PM55 device, and have Windows find it again.  That sometimes helps Windows to use the correct driver.  You might need a reboot for Windows to find the device again after uninstalling.  Let me know how you make out.  Goodluck.

Hi!

I have uninstalled the chipset that I installed with not sucess  but I have not restarted the computer as you say; I look for hardware changes and detect it again but without success. I will try rebooting as you say but I dont see much success ... Then I will comment on whether it went well. I used at first the discs that came with my computer ofc but without sucess.

Greetings

I found the driver here  but that does not work for my chipset. What is the problem?