editing Windows MBR entries

well you can restore the mbr to its prevoius value.
Boot from Cd go into restore mode and run fixmbr command

Cheers!

You can use any of the utilities on this link to wipe the HDD so you can do a clean install of whatever you want. While it is aimed at the selling a used computer end it still applies here.

http://www.microsoft.com/athome/security/update/donatecomputer.mspx

Col

If I understand you correctly, when you boot your PC, you get a screen like the following:

Please select the operating system you wish to start:

Windows XP Professional
Windows Longhorn Setup

Is this correct??

If so, then you can fix this problem easily by editing your boot.ini file. It's located on the root of your C: drive (C:\BOOT.INI). Just open it up in notepad. Just make sure you back it up first! Here's an example of what the file looks like:

[boot loader]
timeout=0
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS

[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional"
multi(0)disk(0)rdiak(0)partition(1)\WIN2K="Windows 2000 Professional"
C:\$WIN_NT$.~BT\BOOTSECT.DAT="Windows XP Setup"

In the [operating systems] section, just figure out which one is your "normal" installation, and delete all the other lines. In the [boot loader] section, make sure the default= line reflects the one you kept, not one of the lines you deleted.

Now, I am not sure where Longhorn keeps its setup files, but I am sure it is in an unusually named folder like $WIN_NT$.~BT or something. Just delete that folder and everything should be back to normal.