So much wrongs in this thread... actually, the title of it should be changed to "Downgrading OS due to confirmation bias"
1. Vista SP2 and Windows 7 SP1 run EXACTLY the same on the same hardware. I've tested it, there is no difference in performance assuming a dual-core processor and at least 2 GB of RAM. (Windows 7 does have an edge when it comes to memory management, and so performs better on 1 GB)
2. If you don't like Vista and like Windows 7, it is entirely because of confirmation bias, you've not tried it with SP2, or you've not tried a fresh (as in no bloatware/crapware from a prebuilt rig) install of it.
3. Windows 7's memory management is far superior to XP's. Windows 7 runs better on 1 GB systems than XP does (assuming either an Intel Atom chipset or a dual-core processor)
5. There is nothing wrong with 2 TB hard drives, assuming they only have three platters, which is the norm for modern 2 TB hard drives. platter and head counts are what increase your chances of failure with HDDs. For the past 1.5 years, though, most 2 TB drives on the market have been 3-platter drives.
6. Partitioning a hard drive has no impact on performances and doesn't break anything. It cannot be a PiTA (in fact, it is the opposite: partitioning system data from personal data can save you many a headaches)
7. IF YOU LIKE WINDOWS 7 THEN YOU LIKE VISTA SP2. Stop calling Vista crap if you like Windows 7, because they are the same (UAC is less secure in Windows 7 by default and they gave it some new aero effects, but beyond that, all under-the-hood differences between the two were effectively nullified with SP2, where Microsoft ported a bunch of the kernel changes back to Vista). All you are doing is falling for confirmation bias or using outdated information to make your judgement
10. There's nothing bloated about Professional version of Windows as most of the differing features are disabled by default (with Windows 7 you don't even save hard drive space with Home editions, as every edition of Windows 7 includes all the features of the others, they are just inaccessible without the right key -- made Windows Anytime Upgrade a lot simpler). The one advantage for the vast majority of home users for Windows Professional editions is that it extends the support cycle, meaning you don't have to upgrade as often. In my experience, most people keep their computers going for years and years without upgrading, so it is a very big advantage in my book. It's a shame most people are unaware of this fact (which is why I always push people to get the professional edition on any PC they plan on keeping in the long-run, as it more than pays for itself).
11. Outside of A TechNet license of some kind, you won't be able to find a copy of Windows XP in the modern world
12. There are various reasons to not us XP anymore, but the biggest is the incredibly poor security of the OS. No ASLR (mmm, I do loves me some overflow) and everyone running as admin does that. Tthere are numerous known security holes in Windows XP Microsoft has not patched, claiming it is architecturally impossible to patch them, and it's only a matter of time before a worm abuses these to get installed with zero user interaction.
13. While Win2k was a wonderful OS, going back to it would be the biggest mistake anyone could make as there are countless unpatched security holes for it (I remember reading an article a while back where it was estimated that 60% of still-existing Win2k installs have some malware on them). Don't use an unsupported (and therefore unpatched) OS connected to a network.
14. Going off of the above: I do highly recommend upgrading to Windows 7, despite it not being much different from Vista. Why? Vista Home and Ultimate editions reach End of Life in 2.5 months time (April 10th 2012). After this point Vista Home and Ultimate editions will stop receiving security updates and malware will easily infect them with no hopes of a cure. I recommend upgrading to Windows 7 Professional as otherwise you'll have a repeat of this in January 13th 2015 (less than 3 years away now), as that's when Windows 7 Home and Ultimate editions reach end of support. Windows 7 Professional will be supported until 2020
And while you're at it avoid Hitachi, Toshiba, Maxtor, Quantum, IBM, and Seagate. Oh, and Samsung.

There's so much superstition regarding hard drives...it cracks me up. If you listen to what people say on forums
every brand of hard drive is terrible and unreliable. The funny thing is that over the years that I've been building computers pretty much every HDD manufacturer has had their good and bad models. I guess once someone has a bad experience and loses data they hold a grudge. I can't say I blame them, but you really have to look at these things on a model-by-model basis. No one brand is universally great or terrible.
Aye. The only one I avoid is Seagate (because they haven't earned my trust back, don't think they ever will due to their poor handling of the firmware problem 2 years ago) and any one where there has been a verified and reported incident RECENTLY