Visited local shop and ran ubuntu 18.04 on a C521 with 2 GIGS of ram LIVE from the DVD works fine. XP is not supported by anyone including Microsoft and Dell. Its End of Life End of support. Have someone burn this ISO to a DVD-R at 2x or 4x or 8x max and F12 boot it live. Works on C521 even when hard drive is removed. [URL] If you cant do that then buy a boot DVD [URL]  
My Dell Dimension C521 has Windows XP and it will not connect to an ethernet connection no matter what I do. Ive re-set it up a few times and I'm getting nowhere. I have 1GB/s ethernet from Xfinity(comcast). Any help or ideas is apricated!
Dell Dimension C521 Will Not Connect to Ethernet in Windows XP