Hi,
Assuming you are running windows 95/98 you can edit the MSDOS.SYS file in the root of your hard drive which contains the settings for running scandisk automatically.
This file is read only, so you will need to change it to read/write.
Open the file in notepad (FILE --> OPEN --> C:\MSDOS.SYS)
Change the value of 'AutoScan=' to:
AutoScan=0 : Scandisk is Disabled
AutoScan=1 : Scandisk Prompts First
AutoScan=2 : Scandisk Runs Automatically
Save the file and reboot your PC, if you have set it to 0 then you should find that SCANDISK does not appear again.
There may be another reason why scandisk keeps running, but this is useful if it keeps running but never seems to find a problem.