Svchost and regsvr problem

Hello,
i had regsvr.exe and svchost.exe corrupted wit viruses.. i moved them to avast 4.8 chest. bt athen wen i start my pc , evrytim it wud display a message"regsvr.exe" not found. search using a keyword....".
i again restored regsvr.exe file from avast chest..
startup problem gone bt still regsvr.exe in system32 folder is identified as virus..
wat to do wit this problem??
n wit svchost.exe??
please help urgently..