Microsoft KB article on svchost.exe on WinXP Pro SP3
From what I can see, svchost is needed by EventSystem, Netman, NtmsSvc, RasMan, SENS, TapiSrv, and RpcSs. If you're not having issues with anything, and just getting the warning, it might be something tolerable. However, it wouldn't hurt to do a few scans.. If the file is corrupt in some way, it could (hopefully) be easily diagnosed by a fairly quick System File Check. To do this, go to the command line as an administrator and type "sfc /scannow" . It may need a copy of a Windows XP SP3 disc to do any repairs if it finds issues.