Sorry but I run an IIyama Provision E2710HDS screen and an IIyama 1902 Both aren't an IPS panel and are neither cheap or nasty.
You could run windows XP but to be honest you'd struggle to find drivers for the 64bit version. Forget Vista 64bit for the same reason. I've had both and they aren't well enough supported.
I now run Windows 7 64bit Home premium. The higher versions don't offer anything more for the average user. If you buy the full version you will only get one DVD in the box, either the 32bit or 64bit. The full versions don't have both dvd's.
It will cost you £73 form Microdirect for a full legit version. Your better off formating and starting again than upgrading. I have been to no end of pc's where they have gone the upgrade route and had problems.
http://www.microdirect.co.uk/Home/Product/42562/Microsoft-Windows-7-Home-Premium-64Bit-OEM
Up to now I haven't changed my drives which are all Maxtor drives. I run a 320gb for my filesystem and programs, and 2 x 500gb drives for data.
This is the only thing in my machine I'd consider upgrading to a faster alternative. It's very much horses for courses but Samsung won't be on my list of drives.
Before you go buying 1tb drives be aware that the highest number of drive failures tend to be 1tb and above.