I got this server for free, it was quite interesting to have fun with it!
Do you have any idea on what I should install on this thing ?
2004 hardware -> dumpster! Seriousky, with the electricity bill of 1 year of that server running 24/7 you can buy a used Dell, HP or Lenovo PC (2/3 maybe 4 years old); you will have more power, way less power consumption and way less noise.
Please, first, start by reading the article… Stop wanting to throw everything in the bin, old hardware are still relevant to learn how the world was made of in the past. Would you say to an archaeologist to throw the 2000+ years old pan he found because he can get a new one for cheap online ?
An archaeologist would not use the pan, they would study it and put it in a museum.