These are the current specs of my 'ultimate' Windows XP rig. I specifically tried to build the fastest possible 32-bit XP machine, but still maintaining as much compatibility as possible.

As I understand it, it's possible to go higher spec (e.g. 4790k) under Windows XP, but at that point compatibility becomes more of an issue.

I haven't yet dual-booted this system w/ Windows 7, but I imagine it would have no issues (I used to dual boot an E8400 rig with XP/7 ).

MB: Asus P8Z68-V Pro/Gen 3 motherboard
CPU: i7-3770k CPU
RAM: 2x2GB DDR3 RAM (Corsair XMS3)
GPU: eVGA GeForce GTX 980Ti
Audio: Creative Labs X-Fi Titanium Fatal1ty Champion
Storage: 250GB + 500GB Samsung EVO 840 SSD (dual drives)
Removeable Storage: LG DVD Rewriter
Power Supply: Seasonic 750W Prime 80 Plus Gold
Case: Fractal Design Focus G
Cooling: Be Quiet Shadowrock 2 Cooler, 2x Corsair ML120 120mm fans (CPU cooler/rear), 2x Fractal Design 120mm fans (front)

After much deliberation I've decided to go the small form factor route on a dedicated XP machine using the HP Elite 8200 SFF.

I'm currently working on some hardware upgrades for it and should wind up sort of like Phil's system here:

https://youtube.com/watch?v=C5QjZJvook8&feature=shares

If I get it locked down I may try dual boot Win XP\Win 7.

I'll keep this thread updated as I push along.

My triple-booting (DOS/Windows98SE, WinXP, Win10) ultimate all-arounder has:

Asus A8V Deluxe (last VIA chipset which supports PCI-DMA so SB PRO support in DOS with ESS SOLO-1 PCI sound card)
Athlon 64 X2 4200+
2GB RAM
Radeon 3850 AGP
Voodoo 3 PCI
Audigy2
ESS SOLO-1

Well, here it is.... my new XP rig all set up.

Upgraded with an SSD, 4 GB RAM and a Radeon HD 7750.

Plays Far Cry on max settings smooth as silk.

Overall it is based on a rig I saw over on Phil's Computer Lab.

(Darn you Phil.... Stop giving me ideas to spend money on....)