hard drive with a different OS

"Be careful with these - they do not support SATA III natively! You need a drive with full I/II/III support - ideally. If you can find one with II/III support, you’ll probably be in okay shape. Unless you have a fully legacy compatible drive, it can be hard to find one unless you install a SATA controller card which supports it to bypass the nVidia northbridge. I can’t find anything direct from HP, but I strongly suspect it’s SATA II based on other boards known to be at that level. However, HP did have a bad habit of crippling their BIOSes Option ROM configuration in the name of “compatibility”.

Find a cheap SSD with at least 256GB (or within the 256GB class, like 240/250GB) with SATA II support and install that on the DVD drive connector - USB externals are cheap."