Various things to check here:

• Check the 'hinv32.log' to make sure Hardware Inventory is actually running. If it passes the file to the Copy Queue Manager then it should next arrive at a 'Cap_Sitecode\inventry.box' directory. From there the Inbox Manager Assistant copies the file (it will be a '.nhm'), to the Site server in the '\SMS_Sitecode\Inboxes\Inventry.box' directory. Then on to 'dataldr.box' and into the database.
  
  If there is no 'hinv32.log' then the Hardware Inventory agent has not been properly installed (hence the mysterious lack of hardware inventory). Check to see if there is a 'INHINV32.LOG'. If this log isn't present then something is preventing hardware inventory from even being scheduled to install. If the log file is there entries in the log should tell you why its not installed.
   
• Check that the client has at least 30 MB free disk space on the partition where Windows is installed so that the hardware inventory agent can be installed.
   
• Check if there is anything in the '\BADMIFS' directory.
   
• Check for anything 'out of the ordinary' in 'CCIM32.LOG'
   
• Check that the domain 'SMSCliToknAcct&' account isn't locked out
   
• Check that the Registry on the client isn't full
   
• Check that the Service account database isn't locked (try to go into 'Control Panel | Services' and see if you can access anything)
   
• Look in the 'SMS\inboxes\ccretry.box' directory on the Site Server to see if there are files there and if so open them in Notepad and look for one (or more) with the NetBIOS name of the problem client. There should be a error code ( I forget the exact text) from the last attempt to install the client software. Use 'Error32.EXE' from SMS tools to give you some insight to the error code.
  
  The CCRetry cycle is once an hour (for 256 attempts), that is why you will see an hourly sequence to your logged events on the client.
   
• Also what folders are in your clients '\ms\sms\clicomp' folder (does this folder even exist?)
   
• If this is an NT client check how many folders there are in the '%WINDIR%\SYSTEM32\WBEM' directory compared to a working client.