I've been an IT engineer and tech support guy for almost 20 years, and I'd be very surprised to find XP *now* running better than win 7.
Sure vista was a pig, and folks stayed with XP while that was out, but the only reason to keep XP now, is if you have software or a device that's not supported by win 7.
Going back to XP removes a lot of the more modern security changes, and will open vulnerability to a lot of crap that win 7 just ain't prone to.
If your system is quad core and over 2gb ram as stated, it's odd for win 7 to be glitching, I've had it running smoothly, if a bit slowly on far less spec.
Are you using a free anti virus or McAfee? I've seen both cause Explorer crashes. Also some cataloging apps or perhaps unusual hardware with a very bad driver. It's hard to give and definite answers from so little info, but going back to xp is a bad idea. I've used 7 since it was out, 8 is imo not worth the upgrade unless you have a touch screen.
If you want to pm me with further details I can see if I can give you some ideas, but I'd suggest a malware scan (malwarebytes anti-malware is a great free program), and changing your antivirus to Kaspersky or Norton or one of the other "pro" ones.
The usual cause of Explorer malfunction is malware or software that corrupts it's processes.
Sorry I can't be more help.
Nic.