I prefer Logitech, as they just RULE! I am unfortunately going to have to leave XP behind due to the security holes that will be due to no more support for it, & I REALLY don't wanna use any newer versions of Windows as they suck so much! I'm also wondering what other HW will or will not work under Linux Ubuntu, as I built this system in Jan. '12, & spent a tad over $1,300 doing so, & cannot afford to build another one right now. I also cannot seem to find any info anywhere that is actually helpful on this, & I can't write, or rewrite code to get any existant drivers to work under Linux, as I am no programmer, & don't understand any of that stuff. Please, any help is immensely appreciated. TIA.

They will probably all work. Download the liveCD and try that as a "Test Ubuntu" - it runs from the CD rather than installs itself. That way you an be sure (all) your hardware works o.k. before going ahead with the install.
Instructions on how to download/burn on the Ubuntu site - can be done from XP.

have a look here https://www.linuxquestions.org/hcl/ under I/O Devices heading you'll find keyboard and mice that have been reveiwed and tested. Not sure how up-to-date it is, but it's a good starting point. Most keyboards and mice will work, it's when you have gaming gear that uses software to help support it's functionality that it requires you to investigate and check if it works on your chosen Linux platform.

i have yet not had a mouse or keyboard not "just work"

now some "fancy" Microsoft Windows keyboards have a "my Documents" key or a "email" button or a Microsoft Media Player set of buttons
those buttons might not work .

but almost all should work .

Same here... I have at least 50 different wired keyboards and a dozen or so wired mice, and none of them have failed to work under Linux.

Good luck with it, EJC-74!

From reading around I think you are more likely to have problems with Bluetooth mice and keyboards than those which use proprietary technology, oddly enough. I've not come across a wired or wireless mouse or keyboard that hasn't worked either.
There was somebody on this forum who found what seems to be a fault with a specific USB chipset but it's a rare thing to see.