That I should get such tax money !
What you can do with your present HDD depends on what your son is going to do. If he is going to buy or build a complete new computer then your best and simplest bet is to persuade him to hand you his present one complete and intact - obviously less his personal data etc.. If a monetary consideration for this would be inappropriate then perhaps a bottle or two of sipping whisky might do the trick.
If this is what happens, then you won't need your HDD to run it, but you could install it as a secondary drive for data storage and you would have no problems with changing operating systems, you would just use the OS that is presently on the computer.
If however he intends giving you this computer minus hard drive(s) and possibly other bits and pieces, then I can be 99% sure that your OS will not work in it. Apart from the fact that your hard drive doesn't have any of the drivers for his hardware on it, there is the problem of the Windows licence.
There are two types of Windows licence - retail and OEM (Original Equipment Manufacturers). If you have a retail licence then you can transfer it from one computer to another, but I suspect you have an OEM license and these are tied to the motherboard and cannot be moved from one computer to another. So, try hard to persuade him to give you the computer complete !
If he is unable to give you computer complete, then you can use your hard drive in it, but you will need a new copy of Windows and you will need to install all the drivers needed for his computer. These include the chipset drivers and all the others - audio, video, printer and so on.