So I have a Dell Vostro running ubuntu 9.10 and Windows 7 in a dual boot that was working fine...

...until this morning. The problem occurred after I joined the Windows side to the domain here at work. (I don't know if that matters, but it is the only thing I'd done differently.) When I went to restart the machine, I got the Dell intro screen, it went blank, then back to the Dell intro, blank... and cycled this way until I held down the power button and put the poor beast out of its misery.

So I booted from my ubuntu install CD (which happens to be 9.04) and re-installed grub. After that, the system was back to normal. I didn't even have to re-edit my menu.lst file.

So after doing some work in Linux for a while I went back into Windows to do some file transfers and when I restarted to go into ubuntu... *croak* same problem. Same solution. Couldn't get to the grub screen to boot into either OS, as before.

But now I'm afraid to go back into Windows. Does Windows 7 kill grub normally? Only when it's in a domain? Is my machine possessed?

I am going to guess that when you connect to your network some kind of scanner detects that NTLDR has been removed from your MBR and "fixes" the problem.

You can always change it so that you copy the GRUB loader to a file in the root directory of your Windows 7 installation and add a menu item to the Windows boot list for Linux using bootcfg.

I have the same setup only on an Acer Aspire One and never had this problem. In fact I would wager it's the most popular dual-boot combination there is at the moment so I wouldn't look for some bizarre conflict between Win 7 and 9.10.

You mentioned that it goes into a reboot cycle and never gets into GRUB? The first thing that would tell me is a hardware problem; but with GRUB reinstalled it works fine until you boot into the other OS...did you install GRUB to a partition or the MBR? That may cause similar problems. Keep in mind that a Win7 install actually uses 2 partitions, one for "system" (what we would call "/boot") and the main partition (or our "/"); are both of those still intact? Dell might have their OEM system restoration partition on the drive as well which could be screwing things up.

I would get a Parted Magic liveCD and find out what's going on with the partitioning scheme first.

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I've been experiencing something very, very similar on four-year-old HP-Compaq. Every time I boot from Win-lost back into *buntu (I've changed from XFCE to KDE and back again in order to cover my bases - there is no problem happen in Debian/Lenny [5.0]): bang: hangs at "Grub loading..." until it either shuts itself off due to high temp' or I do it through frustration...

I believe there is something going on re: auto-fixing of the MBR, but I think it's a Windows component not my security software. Unforunately it may have been something I activated too, but I've no idea what or what for, sadly.

I have XP on my afflicted machine, so your:

Idea makes sense, even though I definitely installed to the MBR. My last hope (before going to Debian || doing some major surgery on the Grub2 installed) is to follow a guide by "Herman" that claims to not move the boot sector or use Grub2.

See my question regarding this issue on Launchpad.net for more information.