BSOD on WindowsXP with Motorola SM56 drivers

Here's how the things a
- I have 4 different modems - all Motorola SM56 but each with different
features
- These modems are inside 4 PCs with WindowsXP, two with Duron, two with
Celeron inside
- All 4 modems work with drivers from Motorola on Duron based machines
(tried each one on each PC)
- None of these 4 modems can be installed nor work on Celeron based machines!

What happens on 2 Celeron PCs is that driver installation results with BSOD
(I've disabled automatic restart) where it says STOP: 0000007E.

More on the matter, one of Celeron based PCs has only SP1 installed while on
the second one is clean installation of Windows XP with SP2. And that doesn't
help. In fact, on another two Duron based architectures XP is not the "clean"
OS installation, yet modem driver installs normally and modems are working.

I've tried disabling onboard soundcard, removing all cards out except
modems, checking with different drivers available on Motorola site - and
nothing works. BSOD is what I get every time.

Then I've tried Dell's drivers (not ment for these modems). Installation of
these drivers never generate BSOD, and I confirm that Motorola SM56 modems
work with these drivers. However, again ONLY on Duron based machines! On
Celeron ones these drivers return errors?!

Am I crazy or what? The only thing I'm left to check is Mainboard BIOS
updates. All 4 Mainboards are Matsonic's, not the same ones though. Each PC
has different mainboard inside. The only similar thing on mainboards are VIA
chipsets, but I've installed latest VIA's drivers on all 4 PCs.

What are my options? To buy new modems or to try with BIOS flashing. I'd
like to keep Motorola modems, but I'm not very happy with the idea of
meddling with BIOS. Anyone has any other idea?

Just to mention that modems worked perfectly on all 4 PCs while win98 was on
those. That's why I suspect that the problem is WinXP/CeleronArchitecture and
not something else.

P.S. 4 PCs are not mine, only one is mine, other 3 belong to friends of mine.