"I have two installations of XP on the same partition........"
1. Boot to the desired version of Windows XP you want to keep. Making note of the position in the boot menu. This will be important when you edit boot.ini.
2. Open a command prompt * and type " echo %windir%" without the quotes. This will give you the current Windows folder you are using.
3. From Explorer, delete the folder containing the installation you want to remove. The original install folder is usually called Windows and subsequent folders will be derivatives of Windows or Winnt.
4. From System Properties [Winkey+Pause/Break] > Advanced Tab > Startup and Recovery > Settings > Edit.
5. Select the Edit button and from notepad, first backup boot.ini, by going to File; Save As and rename boot.ini. to something like boot.inibak.
6. Remove the line referencing the installation not chosen; you made note of in step one.
7. Set timeout=0 so the system boots directly into Win XP (you will not get the boot menu).
8. Save As boot.ini & Exit.
9. Reboot.
* To access the command prompt: Start>All Programs>Accessories>Command Prompt or from Start>RUN>Type "CMD" without the quotes, then press OK.