URLscan is usually located in the directory C:\Windows\system32\inetsrv\urlscan. Navigate to this directory and edit the urlscan.ini file. By default, this file has the entry:
MaxAllowedContentLength = 30000000
which restricts the maximum allowed upload size to 30 MB. Changing this entry to a larger value will allow the server to accept large uploads. You may need to restart IIS for changes to take effect after saving the file.