Welcome to the forums :emotion-21:     You won't have any problems installing a retail copy of an OS. But as you've found out, you'll subsequently no longer be entitled to support from Dell.  They only provide support for the OS which was pre-installed on the system. As for the "proper procedures":  It's no different to doing a 'clean' install of an OS on any other system. Official Microsoft (with screenshots) Install Windows XP Paul Thurrott's 'Windows XP Clean Install (Interactive Setup)'With screenshots Install Windows XP Dell's own 'Manually Reinstall Your Operating System'   Just make sure you have all the XP drivers you need, before you start the installation :emotion-55: Burn them to CD/DVD, or copy them to a pendrive/external hard drive, so you have them handy when you've completed the OS installation. I'd also advise downloading XP SP3, and doing the same with it. Then all you'll have to do after you've installed all the drivers and SP3, is run Windows Update.  You'll probably save yourself a couple of hours doing it that way  :emotion-5:
Dell support will not assist with the installation or support of any non Dell branded OS CD on any Dell systems purchased.  I am hesitant to proceed with a fresh XP Pro install on my Dim 4300 if the unit will not function properly due to Dell's proprietary bios versions, drivers, etc.  Can anyone shed some light on this and advise proper procedures to follow.  We have a couple of units to forcefully upgrade OS to XP Pro.  Thanks.
installing a legal retail XP Pro on a Dim 4300, or is the Dell branded OEM 
required?