Can you recommend a controller card that would work with my motherboard and Windows 10?
I would try the present controller card before making any purchase as the specs say it is compatible with 64-bit versions of Windows, the card being around from the days of XP is why I mentioned my concern.
My C drive is a partition that's 34Gb in size, but it can be enlarged if necessary.
Nowhere near large enough, any new build that I do will now have a minimum of a 240/256GB SSD (dependant on what is the best price at the time) or a similar size partition on an appropriate capacity HDD.
4GB of RAM is fine for Windows 10 64-bit but to get the best out of a 64-bit OS 8GB of RAM is recommended, adding a further matching pair of 2GB sticks would be fine as and when your budget will allow or depending on how long ago your purchased the present 2GB sticks you may be allowed to return them and swap them for two 4GB sticks.
Being in the UK your link does not work for me but fwiw best that I could do was here I suspect for $79.00 that you will be getting a digital download, is that correct.
I can format my C drive and do an install of Windows 10 as soon as I get the disk and other required hardware.
What is the capacity of the HDD that you will be installing to.
You can actually download and trial Windows 10 (Enterprise) for 90 days before making any purchase, see info courtesy of Andre Da Costa at the link here
Tip, when the time comes to clean install Windows, disconnect all other storage devices other than the HDD that you will be installing to, this to remove the possibility of accidentally installing Windows to the wrong drive.