Next time please quote any error messages exactly. If you received an error message with the actual file name "synchost.exe" and this is not a typo for "svchost.exe", then your computer is infected.
Be sure the computer is clean:
http://www.elephantboycomputers.com/page2.html#Removing_Malware
Post back with the results and the text of any error messages for further help.
MS-MVP - Elephant Boy Computers - Don't Panic!