If you compress files to save space Vista will also compress the bootmgr !
This means that you can no longer boot it up! very clever, only Microsoft could make such a dogs dinner of something like this.
I also then experienced problems making the computer boot from CD.
I finally managed this and used the repair facility on the Vista CD, it assures me now that Vista is working fine.
However when I try to boot up I get this message

Caution: This hard disk may be infected by virus!

Thats it I can't go any further.
Does anyone have any ideas as I am completely out of them.
Any help would be massively appreciated as the thought of losing everything in a complete re-install is unthinkable. Thanks in advance.

Well I haven't used vista but it seems like the standard fixes should apply. Have you tried to go in via safe mode? If that doesn't work, can you use an enclosure or another computer to try and get your files from that hard drive? I suspose if the files are really important to you and you have no other alternative you can always take it to a computer repair shop and ask them to get the files for you. Of course you've already thought of this but it sounds like a reinstall may be necessary. Doesn't sound like compressing files if very user friendly on vista. I'll be sure to keep that in mind if I ever use vista. Thanks and sorry for your troubles.

Reinstall. That's the only way to fix the boot. And you will have to boot from the CD to do that.

Never compress files.

What about recovery console and running fix /mbr ?

after a recent new install of vista i get the 'cant find bootmgr' error and i havent compressed any files!

anyone know why?

If someone else use the computer may be they have done it for ya. if not then may be doing a repair from recovery disk might work for ya mate.

Regards
Raj

use supergrub its good at fixing boot problems and it is vista compatiable even though it doesnt say it is or just insert your vista dvd go past the language selection then click repair see if that works.

I really hate to be the bearer of bad news but I just recently had the exact same problem. Vista messed up and I used the vista recovery DVD and when I restart it says

Caution: This hard disk may be infected by virus!

And I was at a loss. I tried everything, even when there were NO PARTITIONS ON THE HARD DRIVE it still gave that error. Well I reinstalled vista, restarted and it still gave it. I wasn't happy. I actually smashed my hand down on my keyboard... And lo and behold. Vista booted.

What you say? Vista booted?!?! Yes, it turns out that the whole time if you press enter (or any key I believe but I endorse enter) that it just passes that error by.

I for one would really like to know how to get RID of the error that seemingly integrated itself into the bios... but I can at least leave with it.

Hope this helps!

no it hasnt. Your motherboard is an idiot

Go into your BIOS and turn off MBR/Bootsector Virus Protection (may be named differently)

bsically some BIOSES prevent things writing to the bootsector but this is BAD if you are installing an OS as the bootloader meeds to go there

vista is crazy