InvalidError is correct. It locks it down to the CPU ID and possibly the mainboard, but other components should be upgradable.
However, when getting a copy of Windows, exercise extreme caution. I purchased a Retail copy of Win7 Pro from an eBay seller. The packaging, even when delivered, looked legit. I paid the full price of $210, so it wasn't like I was looking for a deal. I installed it on a PC a couple of weeks later and then 30 days after that, a message popped up stating that I had only one more week to use this Trial Version of Windows. The seller on eBay disappeared. I contacted eBay and was told that there was nothing they would do, because it was over the 30-day reporting period. I contacted Microsoft, to report how deceptive the packaging was, since it gave no indication that it was a Trial copy. They said that many people have been burned online by this scam, and they sent me a special copy for use on that one machine. So, while I got a working copy of Win7 Pro, it is effectively locked down like an OEM copy to the machine it was installed on.
I was looking at other software online too, and many try to pawn Educational copies of software as equal to Retail versions. Don't believe that for one moment. While they may run similarly, they often have licensing, use, or verification restrictions.
I will never buy software from an online auction house again, or website stores that have a marketplace where multiple sellers participate, especially the ones that are in financial difficulty, This also includes the website having the smile face boxes, since I've received used merchandise under the guise of being new there too.
I bought a PC for my son from TigerDirect, not knowing that 5 weeks later they were shutting down. After several weeks of not getting my PC, and asking for a status, I was told that the company was going down and I would probably loose my money. I found out the holding company of TD and contacted them directly, letting them know how my son's money he was saving, along with my contribution was going to be stolen by TD. They sent me a refund in 2 weeks, but that was a scare. Check the stores you are buying from, and if they are floundering, you might not get what you think you are buying.
Years back, when PCs were expensive, I paid $3,000 for a machine and it had a problem. It was under warranty and I was told to send it back. They too were failing, and when I called over and over, they sent me a machine that was only worth $800.