A well and in good condition PC will not hang up running scandisk.
Your first priority is to make sure that nothing you can't lose has a copy elsewhere on CDR or what backup you use.
After this, check the Shutdown Article at http://www.aumha.org/articles.htm if you are having issues shutting down proper.
Next boot SAFE MODE and run the scan again. SAFE MODE must complete or you need to fix the machine.
I have Windows ME. Every time I boot up, the ScanDisk panel appears saying there was an improper shutdown, even though I always shut down properly. I once tried letting the thing do its scanning, but it works very slowly; it took hours, and finally hung up the computer. How do I get rid of this thing?