Defrag Time for 20gb HD?

My problem began when I tried to install Corel’s WP Suite 8. I keep getting error message that there is insufficient disk space. I have 8.31gb free space in a 20gb HD; the program requires 50mb free. I then decided to defrag my HD–which brings me to my question. How long should this defrag operation take? It has been running continuously for the past 12 hours and says it is only 5% complete. I am running Win98 on a system (500mhz/256mb RAM). Should I give up or just use more patience?