The second family PC and technically my first actual Linux PC. It ran Windows XP, at one point booting Ubuntu Linux via Wubi (the "Ubuntu in Windows" tool they used to have! which would install Ubuntu into a loop image on the NTFS filesystem and use Grub4dos to boot it).
After the mainboard got fried by a lightning strike, it was replaced with one with a Pentium 4 board (Snow 1.5) which was… more of a space heater than a CPU. Eventually, a while after it became my personal desktop, I turned it into a VirtualBox VM Snowclone on Blizzard – it still takes care of the XP-only flatbed scanner.
This was the first PC I've ever had (or rather, our first family PC). It came with Windows 98 and Windows 2000 pre-installed in a dual-boot setup, and a CRT that did not support EDID (which eventually led to its demise).
At some point, I managed to break the Windows 2000 half and had to learn how to install Windows XP; it took two nights to download the .iso from our ISP's warez site over ADSL. (Yes, our ISP used to have a warez site.)
It had a C-Media audio chip and came with one of those "audio rack"-like control panel apps, and most importantly with a set of "C-Media C3D HRTF Positional Audio Demo" minigames that were probably the only 3D games it could run.
Running a Knoppix live CD on this machine (or its successor, I don't quite remember!) was my first introduction to GNOME and KDE; later I somehow acquired a SuSE live CD that decided to boot at 1600×1200 and lasted about two minutes until it fried the CRT.