There was an issue with XP where that could happen and I believe with SP3 it was resolved.
I still recommend on XP that setting affinities for certain programs ie encoding programs is a good idea but with Win7 and also newer architecture on modern HT processors that is really no longer an issue.
It is funny that my old Dual Xeon P4 based SMP rig with HT will bench close to my COre2Duo on rendering.
If the program is running multiple thread that utilize different resources on the CPU then it is very efficient but if the threads are trying to use same resources than the gains achieved are minimal.
Overall running HT on modern CPUs with modern software will almost always show a gain in performance.
HT keeps the CPU more fully occupied with less down cycles.
A nice I7 with HT being used is a beautiful thing.
Especially how well the OS responds while running multiple apps.
Though I only know this in theory since I am running a Core2Duo
It really depends on usage of computer.
In gaming computers it is not really crucial but in workstations running rendering/encoding software it is a huge performance increase.
There is a freeware program called SeeSaw that in XP was very useful especially for SMP rigs but now with Win7 I havent found a need for it.
BTW does anybody feel that Win7 is kinda like Vista with a SP3?
It is funny that I was in the hospital for my wifes operation and all the sytems there even though designed for Vista were all running XP!
Even now I am hearing that Windows 8 is going to borrow heavily from Mac OSs.
I feel like M$ is getting stagnant and not responding to the latest trends,
They should be looking at the hackers who are hacking Kinect and see what technologies they can buy out.
It is like they have run into a tech plateau and are not respondin well to the changes in tech that are happening.
Between Kinect and touchscreen systems combined with advanced voice recognition they should be coming up with something radical.
Win7 is an awesome OS but not any kind of radical departure.
IMO faste processors are not the answer.
It seems extreme multicore sytems with improve arch with well written multithreaded programs is the way to go.
Amd might be behind Intel in performance for now but their focus on hexacore chips is really the way to go.
For the mainstream market incredibly high cpu speeds are nice but software development utlilizing many physical/logical cores utlizing more on die instructions sets and larger caches really is the more logical way.
Dont get me wrong getting over 4ghz on air with some cpus is nice but I would
rather have a slower 6 core for what I do.
I mean if you are a gamer than just get a E8400 water cool it and get it to 5ghz and slap on a GTX 580/hd 6970 and your fine.
But if you want to encode/do office work and also play a game than a 6 core setup is ideal.
I come from the old days where you had to basically only had to run 1 or 2 programs at a time.
Now on my lame C2D 2.4 I can have multiple IEs open,outlook open,photoshop,publisher and word plus do other apps and stil l experience allmost no lag.
I am a big fan of multiple extended displays and multitask between them.
Really five years ago SMP cpus could hancle alot of that back them just a litlle be slower.
This thing is now that the future looks like everybody will have "web appliances" which will primarily access cloud computing resources over the web.
But what it really comes down to is being able to handle the most threads at one time efficiently.
More physical/logical cores the better.
Software devs are starting to code more and more heavily even in games.
There is a heat disappation (sp) barrier that cpus hit that using multicore setups arer the way around this obstacle.
Sorry for the book