PinguyOS on external hard-drive boots to some computers but not others

[Phossy]

I've installed Pinguy OS directly onto a second hard drive in my main PC - works like a charm, the world is good.

Installed another copy (64 bit) onto a fresh Portable hard-drive so that I can take it on business trips, use on other computers etc., but the darn thing gets picky about what it will boot on.  Works fine on wife's laptop and work-laptop, but doesn't work on either of the desktops we have in the house - any thoughts? I select which drive from which to boot, booting continues but it never ever gets to the grub menu - just gives me a black screen which then lightens after a few seconds (still very very dark) and the computer hangs and needs a hard reset.

Having spent the best part of three days fiddling, googling and banging my head in despair I need divine intervention - any one able to  offer any? 

[Pinguy]

If I was going to put Pinguy OS on a Portable hard-drive to take around with me I would use the 32-bit instead of the 64-bit as the 32-bit will work on nearly every computer ware as the 64-bit will only work on 64-bit systems.

[Jeff]

Maybe this is a stupid question - but just to confirm, both the desktops you are trying to boot it on support booting from USB drives and have said feature enabled in their BIOS? I know many desktop systems do not.

~Jeff

[Phossy]

Yes they all boot from USB.

Chose 64 bit as the computers I want to use all are 64 bit.

I was wondering if it was a Windows 7 issue - it struck me that the XP and Vista machines work, but the windows 7 ones don't.

[Jeff]

I was wondering if it was a Windows 7 issue - it struck me that the XP and Vista machines work, but the windows 7 ones don't.

Non issue. Booting from a device is all hardware level, occurs before the operating system even starts.

~Jeff

[Phossy]

Ok - slight update. Got one more PC to work by updating the Grub file (on the subject of which why is Grub 2 called 1.98..), but one remains immune to booting. Can get to the Grub menu now by holding down shift as it boots, so the PC is obviously trying to pass control to Grub. Looking at the entries in the Grub menu, it assigns root as (hd1,1) however according to GParted the disk is sdc1  (which equates to (hd2,1) . The thing still hangs when you then proceed.

Starting to wonder now if this problem started after Grub was updated in a recent  'auto' update.

[Jeff]

Ahh actually it sounds like the issue is with there being a different number of hard drives in each system (Correct me if I am wrong).

For instance on a Unix system the first drive is sda1, then sda2, and then sda3 ect.

When grub boots from a drive it has an assigned drive number (such as you are showing hd(0,1) for instance - which is hd(driver number, partition number)) These will differ on many systems... Not sure on a good solution for this, but it at least explains the issue some.

~Jeff

[Phossy]

That's what I thought, but the computer it won't boot on just has one hard drive and yet it sees the external as sdc - everything else sees it as sdb. It don't make sense to me !( mind you many things don't)