However, HP has posted a document to its support site that shifts the blame right back to Microsoft. "After installing the initial release of Service Pack 3 for Windows XP an error condition can occur," the HP document reads. "The Service Pack 3 update copies an Intel power management driver to the computer that was not on the computer before the update [emphasis added]. During Windows startup, computers with AMD processors may experience a blue screen error."

It cannot be confirmed that the errant driver is, as HP claims, added by XP SP3 to AMD-based PCs. If that is, in fact, the case, the endless rebooting is Microsoft's fault, not HP's.

Is the intelppm.sys driver problem the only AMD-specific reboot issue? Not according to Johansson and other users, who have also reported shutdown error messages claiming that the PC's BIOS is "not fully ACPI compliant."

Users who have seen this message say that their PCs are running one specific motherboard -- an ASUS A8N32-SLI Deluxe -- equipped with an AMD processor. Those same users claim that inserting a USB flash drive or connecting another USB-based storage device before booting solves the problem.

Are some Intel-powered PCs experiencing endless reboots? Yes, say users.

Johansson noted that some users had seen error messages that indicate their crashes are video driver-related. Both ATI and nVidia drivers may be involved, Johansson said.

How can I stop the endless reboots? To break the chain, you may first need to halt the automatic restarts. Press the F8 key when you see the black Windows XP screen and then select "Disable automatic restart on system failure"

Now, try to get into Safe Mode by pressing F8 at the next reboot. You may need to press F8 repeatedly. Once in Safe Mode, follow the steps Microsoft lists in this support document to disable the intelppm.sys driver if you suspect that's the problem.

If that doesn't work, Johansson suggests trying the more advanced Recovery Console, which can be run from the XP install CD if it hasn't previously been added to the PC. For detailed directions on installing and using the Recovery Console, check out this Microsoft support document. Again, disable the intelppm.sys driver.

If your PC is not an HP or Compaq with an AMD processor, your best bet -- in lieu of anything official from Microsoft -- is to read through Johansson's post for possible solutions.

Isn't there an easier way? We're not sure, but you can try to offload the heavy lifting to Microsoft by using the free tech support it's offering for any install or upgrade problems related to XP SP3.

Although Microsoft normally refers users who obtained XP as part of a new PC to the computer manufacturer or reseller when problems pop up, it will provide free-of-charge XP SP3 install support until April 14, 2009. You can contact Microsoft by phone, e-mail or online chat. (E-mail and chat are available only in the US and Canada.)

Details can be found here.

What if I just want to give up on XP SP3 and revert to something that works? No problem, as long as you can regain control of the PC.

Assuming you can stop the endless reboot spiral, you can ditch SP3 and return to (presumably) SP2 by opening "Add or Remove Programs" from Control Panel, checking the "Show Updates" box, then scrolling to the bottom of the listing. Select "Windows XP Service Pack 3" and click the Remove button.

The PC will reboot (again!), but after that, the machine should return to its pre-SP3 state.

Microsoft spells that out for you in this recently-updated support document, which also walks you through winding back to SP2 using System Restore or the Recovery Console.