Ok, here's the facts. I have a Vista laptop from HP (HP Pavilion dv9700t). I got mine direct, but any way you get it should be the same. You will NOT get any Vista backup media. HP only gives you a lame recovery partition on your hard drive. So, instead, you create your own DVD's. HP includes a program on the hard drive that will burn ready-to-use recovery DVD's. Just open the program, insert a blank DVD, repeat for 3 DVD's, and label them as recovery DVD's and store them in a safe location.
Now, if you want to DUAL-BOOT (keep Vista but also get XP, my preferred method), you should use a partition editor (I used Linux GParted) and resize your Vista partition (The free space left after resizing will be used for your XP partition). You can also delete your recovery partition now, as it is no longer needed if you burn DVD's.
Now, regardless of whether you're dual-booting or just flat out erasing Vista, you'll need to customize an XP install CD. The reason is that the normal XP CD DOES NOT HAVE SATA (hard drive) DRIVERS FOR HP'S NEW LAPTOPS. This is the tough part, and I was trying to load stuff from a floppy drive all last night but it just kept on failing. The easiest way is to use nLite to customize a Windows XP install CD with the right drivers. Depending on your model, you'll have to look around to find these SATA/RAID drivers. Burn your new installation disc, stick it in, format your partition (if you're just erasing, you can erase your Vista partition here and also delete your recovery partition, otherwise, if you're dual booting, pick the unpartitioned free space and format that as NTFS).
Now you should have it installed. It should boot into XP, finish installing, and then you'll have your Desktop. Now, you'll want to install drivers. However, you'll need another PC for this, because neither the WiFi card nor the Ethernet card are supported by XP directly, so you'll need to download drivers. I found that looking for "dv9700t CTO" instead of "dv9700t" found me more Windows XP drivers on HP's page. A quick Google search turned up plenty of driver lists for mine, some being on HP's site and others from manufacturers' (ie Intel, Realtek, nVidia, etc) sites. Install the drivers and restart as necessary. Now your PC is running XP.
If you're dual-booting, you'll want to get a copy of the Vista Recovery CD (it's a reduced version of the Vista Install CD that has the Recovery Console in it). You can use this to fix Vista's bootloader. After the bootloader is working, you can boot back into Vista (not XP, it's not bootable at this point). Here, go to your C: (Vista) drive and enable showing hidden and protected OS files. You'll see "boot.ini", "ntldr", and "ntdetect.com", these are XP's boot loader files. Select all three and copy them, then paste them in your D: drive (or whatever drive is your XP drive, mine was F: because it had D: as the CD drive). Now XP is again bootable from its own partition.
Now, you can use EasyBCD to configure Vista's bootloader to have an option for XP. It's pretty simple and there are guides out there. If you want, you can also use Linux's GRUB bootloader and triple boot (what I'm doing) Vista, XP, and a version of Linux (Ubuntu 8.04 in my case). Either way, the bootloader (GRUB or Vista's BCD) will give you a menu with Vista, XP, and possibly Linux entries, you pick which one you want to boot and it loads that OS. All OS'es are independent from each other, but you can access files stored on any of the partitions (access your music that you have in Vista from XP for example).
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OK, having said that, I do think you should give Vista a try. That's why I recommend dual-booting. I for one will tell you that people saying games run better in XP is a total and complete lie. I just did my own little test. I set up Gmod in both XP and Vista, with same settings, on the same map. Without even turning the FPS counter on, I notice a significant performance boost in Vista, it just runs smoother. Not sure why, but it does run smoother and I'd much rather keep playing in Vista than switch to XP. XP is great for compatibility, that's why I'm keeping it, but for performance, I personally think Vista does a better job (plus I have the 64 bit Vista and the 32 bit XP, so Vista supports my hardware better).