I think the blue screen is mainly caused poorly written software driver or operating system instead of hardware.
If you did all possible drivers and software updates, there is not much left u can do.
You might have to back up all your data, somewhere save. Reinstall Windows with PCI plugged in or
install two operating systems side by side, to have your current windows xp, and vista for example, to test if that solve problem.
This way u dont have to delete your current windows xp.
Even better thing to do is to open case, remove Hard drive, put another one in, and install Windows Vista or WIN 7 or Win xp from scratch, on new hard drive, this way u can be sure, that Windows Xp and files on other hard drive is save.
Of course u if u have spare Hard drive.
In my opinion Win XP never was so good.
If u can, get hands on Win 7 or at least Vista.