Yes, I have a Quad boot,Running XP/Longhorn/Vista/And Win 2008 Workstation.
Now I need to remove This LongHorn version and Install another version in its place,But it will mess up my Booting..Is there a way to wipe and D: drive and format it, and then reinstall another version of Longhorn without messing up my boot sequence.. OR can i just install a boot manager Like OSL2000 to take care of my problem?

If your current multi-boot is managed by the microsoft boot manager, it all uses the boot sector on the first partition on the first hard drive. Whenever you install an MS o/s it overwrites that sector - if the o/s is newer or at least as new as the newest currently present, the multiboot will be preserved. If older, only the o/s just installed will be bootable. You don't mention how many drives you have (is it 4 partitions on one drive?) - but if you reinstall Longhorn (why by the way - just pre-release vista), I'm not sure on the outcome as win 2008 workstation I'm not familiar with (thought it was 2008 server..) - but if its 'later' than longhorn.. There are ways to rebuild the multi-boot if its broken by an errant install - just Google to find.

You are (IMO) much better off starting using a 3rd party boot manager (I use www.boot-us.com). In this case you should ensure each o/s is installed with the others hidden/disconnected onto a primary partition. This will ensure each is independent (ie, wiping and reinstalling one will not affect the others - assuming you make sure they're hidden/discinnected again during any reinstall). Then you run the boot manager to set up the boot menu.

Yes, I have a 160 gig Hard drive split into
4-40 partitions. They are in order as follows,
part 1 is XP-Part 2 is longhorn Part 3 vista and part 4 is Win2008..Right now the boot works fine by being able to choose from old/new..
I will look into this 3rd party boot manager at www.boot-us.com
Ok! I downloaded this boot-us and now i have two boot managers, How do I remove Windows boot manager and use the 3rd party?

I was able to fix my boot manager with
Vista Boot Pro..

Not having any experience Longhorn/W2K8... but presumably they both have/use a boot-loader etc. similar in form to earlier NT-style OS; and are backwards compatible?

Presuming so... surely, as you had a four OS (multi-boot) system utilising whichever M$ NT etc.style boot-loader..., all you had to do was simply boot any of the other OS installed and reformat the Longhorn partition (or just delete its contents). The remaining OSs would still have booted etc. OK regardless. All you would have had is an entry in the boot.ini referring the then defunct OS.

When you re-install Longhorn afresh it will backup the boot.ini as is and then create a new one to reflect any changes as necesary...

There would have been no need to run any fixboot/fixmbr routines?

Using an add-in boot-util would work if starting from scratch; but it adds another step into the whole boot-process - not always a good thing? The less there is (overall) in the way of booting - the better; i.e. don't use them unless absolutley necessary?

Vista Boot Pro did not add anything to the boot ini, It has the option to repair the Vista boot and it did without adding anything extra.

trvlr - they've completely revamped the boot process for the current versions of windows - so boot.ini no longer in use once vista/longhorn or whatever installed. There's a (command prompt) program called bcdedit to manage booting options now - but its not 'easy' to use. Vista boot pro is a good freeware front end - there are others. Vista also has boot repair option booting from the install DVD.

Stev:

Appreciate that info; as I sed wiv no experience of Vista etc... (fortunately some might say) so was anticipating I might be litle off overall once they get involved. Useful items though for me to get across anon...