What is it?

mssearchnet.exe is associated with the Trojan virus zlob.D

What does it do?

From semantec:

"When Trojan.Zlob.D is executed, it performs the following actions:

1. Attempts to copy itself as the following file:
   
   %System%mssearchnet.exe
   
   Note: %System% is a variable that refers to the System folder. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   
   
2. Drops the following file, which is a Windows type library:
   
   %System% compat.tlb
   
   
3. Adds the value:
   
   "kernel32.dll" = "[TROJAN FILE NAME]"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionPoliciesExplorerRun
   
   in an attempt to ensure that it runs every time Windows starts... ..."
   

More info and removal:

Read more about Trojan.zlob.D and how to remove it [url=http://securityresponse.symantec.com/avcenter/venc/data/trojan.zlob.d.html]@ Symantec[/url]