The machine I’m using now is an older (circa 2005) Compaq SR1900NX with a 3.3 GHZ processor, I have a couple ~120 GB hard drives in it, it is a 32 bit machine. It is ethernet plugged into my modem (xfinity) but because of WinXP limitations, FTP download fails for anything bigger than 2 gig.
That should be able to run a newer version of Linux than the knoppix you have. Looks like it came with 512mb RAM from the factory so that would need to be increased to run any newer OS.
https://support.hp.com/us-en/document/c00683794
Maximum is 1gb 2x for a total of 2gb which still isn’t great. You’ll want a lightweight Linux. Just do a web search for lightweight linux 32 bit. There aren’t many that will run on a 32 bit system these days. XP isn’t even safe to surf with anymore. Major target for malware and as you say, it won’t run up to date browsers.
Not sure about connecting to xfinity. You’ll have to take that up with them. Is there xfinity software of some sort installed on the machine? Do you or did you ever have to log into xfinity via a browser?
3.3GHz is pretty good but you really ought to think about finding a 64 bit machine. 32 bit is just getting obsolete.
Are you 100% sure that your processor is only 32 bit? It may very well be that your OS only reports itself as that way and isn’t fully using the chip.
I think it’s more than probable that it’s 64 bit. Is this your computer: ?
https://www.newegg.com/compaq-presario-sr1900nx-student-home-office/p/N82E16883107100
It says 64 bit. The fact that this has an integrated ATI chip means that your linux experience is very likely to be a pleasant one. AMD puts a lot of manpower into its graphics drivers and they are open source so they are a positive out of the box “just works” setup.
Since you are using ethernet to plug into your broadband, your experience when using a modern Ubuntu, Mint, and I usually use Fedora or Manjaro, but the point is your experience is it should “just work” as soon as you get to your first boot. That is what you should expect, that’s what I expect when I do a new install or upgrade. Your only concern should be learning the applications, not tinkering with what’s under the hood.
These days Linux is easier I think for the average person than Windows.