Note that many websites have their own advertising, unrelated to adware.
Gratisware is an Internet Explorer Browser Helper Object. Whilst browsing with IE, it occasionally pops up advertising.
Before you can delete the program files you must deregister the Gratisware BHO. Open a DOS command prompt window (Start->Programs->Accessories) and enter (for Windows 95, 98 or Me):
"%WinDir%\SYSTEM\regsvr32.exe" /u "%WinDir%\SYSTEM\CRS32.dll"
Or for Windows NT/2000/XP:
regsvr32 /u "%WinDir%\System32\CRS32.dll"
Restart the computer and you should be able to delete the files 'CRS32.DLL', 'CRS.EXE', 'CRS32.REG' and either 'CRS.OLD' or 'NEXT.DL_' for your Windows System folder, and the Gratisware folder inside Program Files. You can also remove the registry key HKEY_LOCAL_MACHINE\Software\Gratisware if you like