I know the P4 is slower, but the P4 is in my Windows Machine the Core Duo is in my Mac. I always spend more on Macs than PCs ;D
Drhayden, I heard there is a serious flaw with the quad core machines, the only way to fix it is to go to your nearest UPS or Fedex store and ship it to me ;D 
Anyone considering any quad core CPU should consider M$ policy on multi-core CPU, I recall reading something about this a while ago, the Home versions support single and dual core processors. However, for quad core you will need the Professional/Business versions of Windows OS Vista or XP.
Thanks for pointing that out David! Guess I will have to stick with XP when I upgrade my PC to Quad core as the Business and Untimate Editions of Vista are way to pricey.
My Upgrade Plan:
Early 2008: Pentium 4HT → Core 2 Quad(45nm version)
I just bought My Core duo Mac mini last month so it should be good untill 2010 (I keep my Macs until the 3 year warrenty runs out which will be Jan of 2010)
I can’t recall where I read it but it is worth confirming if you were considering one and XP Home or Vista Home. It should be OK with the Pro versions, drhayden1 just says Vista Pro (doesn’t match a vista version) in his signature. He has one of the quad core processors.
its the vista ultimate davidr…my mistake… changed it :
:o
there’s only the home basic,home premium,business,enterprise,and the ultimate
AFAIK all Windows Vista editions support MULTI CORE cpu’s(one CPU with multi cores). However you will need the ultimate or bussines versions to support MULTI PROCESSOR(more than one cpu on a motherboard) configurations.
Home in both XP and Vista incarnations will support dual core, but MS’s thinking is quad core and multi processor are for business and want to extract a premium for supporting them.
@DavidR: From everything i’ve read so far after a quick google search confirms i am right. Multicore cpu’s(there are no limitations on the number of cores) are supported in all Vista versions the only restriction is on multi processor configurations (2 physical cpu’s or more) which are only supported in the bussines and ultimate editions.
http://blogs.zdnet.com/Bott/?p=130
http://articles.techrepublic.com.com/5100-10877_11-6156413.html?part=rss&tag=feed&subj=tr
As I said I can’t recall where I read it, probably one of the newsletters I get, but no mater what you do it would be wise to confirm before going out and buying a quad core solution only to find it doesn’t work.
Ed Bott talks of Dual core (I said it supports dual core processors) and not Quad core. Whilst ExtremeTech shows a chart that indicated ‘Unlimited’ logical cores, unlimited seems strange and even in Home Basic, which doesn’t even have support for some very ‘basic’ functionality. No encryption, scheduled back-up, media centre, etc. etc. so in something this crippled I find it hard to think Unlimited logical cores (whatever that means exactly) is correct. I would hover be very happy if it were but I would like to see this as a Microsoft chart/listing.
http://www.microsoft.com/licensing/highlights/multicore.mspx
[b]Multicore Processor Licensing[/b] Published: November 3, 2004 | Updated: June 7, 2005
This I found some time ago it is an old article when dual core was just about to become more common and if anything it is as clear as mud as it is so old. The new Core 2 Extreme is in fact two core 2 duo processors on the same die so how that falls on to their multi-core policy who knows.
I think virtual cores refers to Hyperthreading
Then how come people are running their quad cores on Vista Home and XP Home?
Another link for you : http://www.pcper.com/article.php?aid=301
That is fine as practical experience will always be better than raw data tables.
Even though this relates to Quad Cores and XP Home Edition, I would like to hope that would be true of Vista Home, even the crippled Vista Home Basic version.
However, with XP Pro and no intention of a Vista upgrade and probably no quad core processor either, it doesn’t even effect me.
I however do plan on going Vista and quad core(i’m sure i am not the only one) so it does affect me 
I just wanted to get this whole multi core thing cleared up for others that may be reading this thread …