If you can't fix this by going into System Properties | Advanced tab | Startup and Recovery Settings button and editing the boot.ini file, it rather sounds as though you may need to get into the Recovery Console, rewrite the MBR and re-create your boot.ini with BOOTCFG.

I'm pretty sure that there is no registry key for this. The registry loads at boot time, so it can't determine which copy of Windows will boot off which partition -- that's what boot.ini is for.

I have done the boot.ini file and been in recovery all with no luck. i tried fixboot, fixmbr, bootcfg the lot but it doesnt change anything. the thing is though in recovery my partitions are listed as an option to logon to (tried the fixmbr, command when logged onto c:\) but i still cant get them there at boot. 

i see what you mean with the reg though. the other partitions will have there own reg! thanks for that i would have started my "alterations"[lol] otherwise.

Sounds really frustrating.  But at the risk of asking an infuriatingly dumb question, what exactly have you tried with BOOTCFG?

Here's what has worked for me:

In the Recovery Console, log on to the Windows installation you want to be the primary one, if you can, otherwise any other installation.

Start by running CHKDSK on all drives.

Use the MAP command to identify which logical device corresponds to which partition. Then use FIXBOOT [drive] followed by FIXMBR [logical device] in turn for each one you want to make bootable.  The correct FIXMBR syntax is absolutely crucial to success.

Then do BOOTCFG /scan to create a list of bootable installations. This will take a while.

Next, use BOOTCFG /list to check that it's found them all.

Now for each of these installations in turn, do BOOTCFG /add.  In each case, this asks for a description, and once you've entered that, it asks for the boot parameters. Usually entering

/fastdetect

is enough to get you going. (You can always add more parameters later by editing the boot.ini file.)

When you've added all of the installations you would like to boot from, you're done. When you restart, you should get a boot menu with the entries you've just added.

Sorry if this is all stuff you've tried -- I hope it's helpful, anyway.

well,

i went through the steps you suggested, even managed to boot to 1 of the partitions, but i kept on trying to fix the other and caused my system become unstable and made the mbr invalid.

needless to say, it went very downhill from there.

i have re-installed windows on one of the volumes, regained the other two back to boot to and am back on track.

thankyou for your help, the steps u said did work, my own stupidity for not leaving well enough alone.

just thought i'd let u know.

thanks again