I need to get rid of Vista completely and convert back to XP. I know how to boot from the XP disk and delete partitions. But is there anything else that I will need to do?I have a new emachines computer with Nvidia graphics card and AMD Sempron 3600+ processor.Thanks!Yes I know how to delete partitions and yes it is possible to completely install XP and remove Vista. I only need to know if there is anything else I'd have to do once I format the partition, install XP on it, once Vista is deleted.

Installing Windows XP / previous versions of Windows after Windows Vista

Introduction

You can install Windows XP over Windows Vista. You need to perform few steps before you can get both the OS running. Earlier versions of Windows used to parse BOOT.INI to load Operating Systems. Windows XP and earlier NT-line technologies use NTLDR as their boot loader. In Windows Vista, it has been changed and now Winload.exe is the boot loader for all the operating systems. This exe is invoked by Windows Boot Manager (Bootmgr.exe)

Windows Boot Manager reads the Boot Configuration Data and displays and operating system list. Boot Configuration Data replaces the BOOT.INI used in previous versions of Windows. Boot Configuration Data is stored in a data file in C:\Boot\BCD. Boot Configuration Data can be altered by a command line tool (bcedit.exe) or using WMI script.


The Boot Configuration Data includes the following entries:
Boot Windows Vista – (using Winload.exe)
Resume Windows Vista – (using Winresume.exe)
Boot earlier Versions of Windows – (using NTLDR)

Why Microsoft has to replace BOOT.INI and NTLDR?

The previous versions of Windows weren’t capable enough to support API call. Microsoft has changed this in coming versions of Windows. Third party vendors now can develop an application and implement the same with Vista Startup process.



So How to do it:

Note You can run the commands in the following procedure by using the command prompt. If you run these commands in Windows Vista, run them at a command prompt that has elevated user rights. To do this, click Start, click Accessories, right-click the command-prompt shortcut, and then click Run as Administrator.

1. Use Bootsect.exe to restore the Windows Vista MBR and the boot code that transfers control to the Windows Boot Manager program. To do this, type the following command at a command prompt:


In this command, Drive is the drive where the Windows Vista installation media is located.


2. Use Bcdedit.exe to manually create an entry in the BCD Boot.ini file for the earlier version of the Windows operating system. To do this, type the following commands at a command prompt.

Note In these commands, Drive is the drive where Windows Vista is installed.


Note In this command, Description for earlier Windows version can be any text that you want. For example, Description for earlier Windows version can be "Windows XP” or “Windows Server 2003."


Note In this command, x: is the drive letter for the active partition.


3. Restart the computer.

More Details -
http://support.microsoft.com/kb/919529



Regards,
Nick D.