dwwin.exe is dr watson an error reporting tool built into windows.
does a restart help any?
if its win xp have a look in start/control panel/administrative tools/event viewer, click the application and system tabs and look for any errors listed and click them for more info maybe may also help.
sometime spyware can pretend to be genuine windows services and processes and slow the system down, have you run a check for spyware and viruses and is windows all up to date?
try system restore to a date all was well if all the above doesnt help maybe.