Yes, you would be able to install the OEM of Windows on your new hard drive. However, you must watch how much you change your computer's confirguration. Often when you register it, your computer configuration will be recorded, and if it changes too much, they will think you are installing it on a different PC. At that time, you'll have to make the toll-free phone call and explain what is going on...that you're not just installing it on all of the computers in your neighborhood. It's not a problem, but can be an inconvenience.
Yes, they come with all of the drivers. On the OEM disk is the FULL version of Windows XP, with everything that the retail disk contains. However, things like icons, the Help center, etc are customized, and extra programs (free or trial) are added to the mix.
Legally, there is some debate. This is copied from the Microsoft OEM System Builder license (which Newegg linked to):
''If the individual software license is a desktop operating system (including Windows XP Media Center Edition),we grant you a nonexclusive right to distribute individual software licenses; provided that each one is distributedwith either (a) a fully assembled computer system or (b) a nonperipheral computer hardware component. A ?fully assembled computer system? means a computer system consisting of at least a central processingunit, a motherboard, a hard drive, a power supply, and a case. A ?nonperipheral computer hardware component? means a component that will be an integral part of the fully assembled computer system on which the individual software license will be installed.''
This means that it can be included with a a complete computer or a major piece of equipment, such as a motherboard, but not by itself or with something as simple as a power cord. Thus, the OEM version of Windows XP being sold by Newegg is probably not completely legit. However, Newegg may have an agreement with Microsoft...something you'll definately want to check into. (Usually I'd say it's illegal and pirated, but Newegg is a fairly respectably company, so I'm willing to give them the benefit of the doubt.)
Also, note that by accepting the OEM system builder license, you are responsible for all tech support...not Microsoft or a PC manufacturer. Also, sometimes OEM software won't work with your computer...such failure isn't guarenteed....it's a risk you'd have to take. (This is all stated in Newegg's Software return Policy.)
Considering all of this, you would probably be better off just purchasing an upgrade to Windows XP from Microsoft...Windows XP Home upgrade is just $99 for those with Windows 98/98SE or Windows ME. You can also get the Windows XP pro. upgrade for $199 if you have Windows 98/98SE, Windows ME, or Windows 2000. (Those who own previous versions of Windows, and those who don't currently own legitimate versions, are not eligible for the upgrade and must pay an extra $100 for the full version.)
Hope this helps,