Slow boot with USB pendrive plugged in

Spartan117 · 07-20-2007, 01:04 PM

My project is almost complete, had my first live test run in the car last night, worked like a charm. Woohoo

One of the remaining issues:
The system boots XP Embedded from an USB pendrive in about 20 seconds. However, if i leave my second pendrive plugged in while booting, windows hangs for a couple of minutes right before the explorer shell starts. I get the desktop and a cursor, but the start menu/taskbar/icons doesn't show up for a couple of minutes.
I remove the secondary pendrive, reboot, and it's fast again.

Apparently this is a widespread problem, however I haven't found any solution to it by searching. Anyone here know a way? (I don't want to remove and plug the secondary drive back in every time i start the car..)

DarquePervert · 07-20-2007, 01:20 PM

Go into the BIOS and disable USB booting if you don't need it.

Spartan117 · 07-20-2007, 01:28 PM

Wish I could, but obviously I need it for booting from the main pendrive

The slow part is just before loading explorer, not in the bios POST phase..

Forgot to mention one thing btw; the secondary drive was once also bootable (though it doesn't have an OS any more). Maybe the problem is that it still has an MBR that says so? Is there any way to delete/clear the MBR?

dupa2 · 07-20-2007, 10:39 PM

you just need to clear bootable flag from partition, but I don't think it's going to help. Windows explorer or some services may scan/update some information on flash drive (secondary), and typically write operation takes some time, depending on number of filesystem updates. You may try to change the filesystem on your flash drive to ntfs, it may help, but I'm not quite sure.

Spartan117 · 07-21-2007, 06:57 AM

Just tried formatting as NTFS now, didn't help. I did try removing the partition completely though, and that worked, but won't do much good

Do you know what services would try to scan/update anything?

One weird observation; if the activity LEDs on the usb sticks are to be trusted, there's no reading or writing going on at all, on any of the sticks, for the few minutes it hangs...

dupa2 · 07-21-2007, 09:36 PM

shell hardware recognition service may slow it down, but should not block actual gui.

There's one more thing to do a test on, try to mark the drive as read only (like cdrom), I wonder what would happen.

Do you have any other pen drive (different manufacturer) to see how is it going to react on.

Spartan117 · 07-23-2007, 03:15 AM

Thanks, but I actually (kind of) figured it out last night

Here's the story:

- The bios enumerates USB storage devices in order by which port they're physically plugged into. I figured out the order by trial and error.

- When windows starts up, it assigns drive letters to removable devices in the same order as enumerated by the bios.

- The problem was actually that the system drive got assigned D:, while the other drive got C: with both plugged in, because they happened to be in ports ordered that way through all the tests. (Can't believe i didn't notice this.) Apparently, explorer doesn't like living on a drive that changes letters.

Now it boots fine with the system drive in a "higher priority" usb port than the other one, so problem solved.

Still though: when a drive is assigned a letter, the unique drive signature is supposed to be tied to that letter through the registry in HKLM\System\MountedDevices. I never could figure out why the "real" C drive didn't keep its letter, even after deleting all keys and letting C be reassigned before plugging in anything else. Cloned keys also started showing up from time to time...
If anyone has some insight into how the MountedDevices keys are treated, do tell