While not common, occasionally we have seen this file get deleted from a PC. Reinstallation of MetaStock should put this file back onto the system.
I believe you can also download/unzip the astsrv.exe from the following if you prefer not to reinstall:
http://www.internetactivation.com/ecosystem/customer/Necessary%20support%20files%20and%20utilities.zipIf you have trouble with unzipping the ASTSRV.EXE into your Windows\System32 folder (or Windows\Syswow64 folder for 64-bit OS's) you will likely just want to reinstall MetaStock.