I have a 7 year old HP computer with Windows ME. There is nothing wrong with it except it won't run I-tunes and there are no fixes or updates for ME.
I am thinking about upgrading to XP. What would I need to do?

The minimum hardware requirements for Windows XP Home Edition are:
• Pentium 233-megahertz (MHz) processor or faster (300 MHz is recommended)
• At least 64 megabytes (MB) of RAM (128 MB is recommended)<-- (which is a joke. I suggest 512 MB minimum)
• At least 1.5 gigabytes (GB) of available space on the hard disk
• CD-ROM or DVD-ROM drive
• Keyboard and a Microsoft Mouse or some other compatible pointing device
• Video adapter and monitor with Super VGA (800 x 600)or higher resolution
• Sound card
• Speakers or headphones

System requirements for Windows XP operating systems

Of course those are Microsoft's recommendations. Every one else, that lives in reality, knows that wont fly!
800 mhx processor or greater 1 gig+ recommended
256 megs mimimum. 512 recommended.
System specs or model # would be helpful.

Dont pour money into upgrading an old computer. You still end up with an old computer!
Dell is still shipping XP (thank GOD!) and their systems are cheap this time of year.

I have an HP Pavilion 7840 with an Intel 766 MHz processor. It came with 64M Ram which I upgraded to 124 just after Igotit. Has a 30 Gig ultra DMA hard drive.

It would work but might be slow.
Might have compatibility issues with devices and installed software like games, cd burning software, antivirus etc.
Do a lot of research before you do this.

The best way to install any verion of windows is a "clean install." That means format the hard drive and reinstall everything from scratch. Is it worth it?

With those spec you can expect to be able to click on an application and then have enough time to not just go and get a cup of coffee but to make it as well while you are waiting. I would look to see if I could find a copy of W2k which isn't quite the resource hog and is still supported by M$. You are still going to be slow with that processor speed and the low amount of RAM.