Very Slow Dell Dimension 3000 – 24hrs to install Win XP

I have a Dell Dimension 3000 that is very very slow. I figured I would reformat my HDD and reinstall Windows XP. However, the install takes well over 24 hours to complete. The Bios shows that 512MB RAM is installed. I tried a new 80GB Western Digital HDD in it and that still took over 24 hours to install windows from a freshly formatted drive. The processor cooling fan is running and has good airflow.

Any ideas? Please help.

Dell Dimension 3000
2.4GHz Celeron
512MB RAM
80 GB Maxtor HDD