Fortunately, there are better alternatives. Auslogics Disk Defrag is a freeware for Windows 2000/ XP/ Vista with a simple interface, that runs much faster than the built-in defragmenter. You can't defragment more than one partion at a time or set advanced options, but that also means it's easy to use. The program doesn't use too many resources, so you can continue your work.
Another good option is Power Defragmenter, a GUI for Contig (a program developed by SysInternals). The software allows you to defragment only a file, a folder, or a disk. You won't see a beautiful map of your disk. It's just a command-line utility that does its work quietly.
If you're wondering why Windows needs defragmenting and other operating systems like Linux don't, this article is a simple answer.