(SOLVED) Can you run main OS separately in a USB dual-boot?

[besonian]

Although there's been quite a lot of discussion in this forum about how to install PCLOS on an external USB drive, I haven't been able to find anything that answers the specific question I have.

A friend's laptop - an old Dell Inspiron 6000 has bitten the dust - the mobo's packed up and the machine is 100% dead. She wants a new laptop but wants to be able to use Windows as she always has done, but at the same time wants a dual boot with PCLOS - she's keen to try it out. All the laptops she wants and can afford have Win7 pre-installed so doing a standard dual-boot is not on - it would invalidate her warranty. The solution I can see - though I've never tried it - is for her to have an external USB hard drive and install PCLOS on that. There seems to be plenty of info as to how to do that, but this is the question I haven't seen answered - if a dual boot is done this way with GRUB on the external drive, would it still be possible to run Win7 on the laptop without the external drive being plugged in? (I sort of doubt it). As all her work is for the moment with Windows, and Linux will be there only as a try-out to see how she gets on with it, she isn't going to want to cart around everywhere she goes an external drive (albeit a laptop SATA in an enclosure) which is there only to provide the boot loader. Anybody know the answer to this?  

[Neal ManBear]

.....if a dual boot is done this way with GRUB on the external drive, would it still be possible to run Win7 on the laptop without the external drive being plugged in?

The answer is contained in your question --> "....GRUB on the external drive." If the windows bootloader has not been overwritten, it is still there. If it is still there, it should work as well as it ever does.

[besonian]

Thank you Neal. I suppose it comes down to my ignorance as to how GRUB works. I'd sort of assumed that GRUB provided a boot-loader which contained all the information necessary for the machine to boot into either OS, thereby by-passing or overwriting the native Windows boot-loader. But from what you're saying it seems that in the sort of case I've posited, the Windows native boot-loader remains intact on the main machine and is activated only if the Linux boot-loader is not. Is that it? Ooer - seems complex. 

[Neal ManBear]

Thank you Neal. I suppose it comes down to my ignorance as to how GRUB works. I'd sort of assumed that GRUB provided a boot-loader which contained all the information necessary for the machine to boot into either OS, thereby by-passing or overwriting the native Windows boot-loader. But from what you're saying it seems that in the sort of case I've posited, the Windows native boot-loader remains intact on the main machine and is activated only if the Linux boot-loader is not. Is that it? Ooer - seems complex. 

It is simple. (While being complex. ) As you thought, GRUB provides a boot-loader which contains all the information necessary for the machine to boot into either OS. However, if you do not install it to the boot sector of the main drive, it will not overwrite what is there. Installing it to the boot sector of the usb drive means that it will work from that drive.

The last part of the PCLinuxOS installation process is installing Grub where you choose and setting up what will be booted -- you choose.

[besonian]

Done! Thank you for that complex simplicity  I shall now go away and practice on a spare machine and external drive of my own. And mark this SOLVED.