TOAD message "Home is Not valid" (Oracle home is not valid)

I was trying to get my Toad running and it was giving me "Home is not Valid" error, This error doesn't give much information and finding root cause was not easy :( . Here is the thing that I was doing.

- My system had Oracle 9 client pre-installed. I installed Toad and it was giving me home is not valid error.
- My need was to also update Oracle so I went and uninstalled prior version of Oracle client. (remember clean uninstall of prior oracle client is very necessary. If you are expert then try to clear registry entry as well which oracle generally leaves after uninstall as well :( )
- After that I installed Oracle 10.2 and then Toad(9.7.2) but it was still giving the same error. I set the Proper system variables(PATH) and also put my valid TNSnames.ora in proper location, but no luck!!   then I uninstalled Toad 9.7.2 and reinstalled Toad 10.6 and after rebooting machine it's working fine!! :)

I hope this helps.

Also, Please note that I also follow below steps after installing oracle:

1. Add C:\Oracle\ORA10_2\BIN to your PATH environment variable
2. Install ODP dlls in your GAC 
3. Restore your project specific tnsnames.ora  to C:\Oracle\ORA10_2\NETWORK\ADMIN
4. If you are accessing Oracle from .NET web applications running on IIS 5, give IIS/ASPNET permissions on  your Oracle folder
     a.    Grant ASPNET user read/execute permissions on C:\Oracle\ ORA10_2
               i.    In Windows Explorer, right click on the Ora10.1 folder and select Sharing and Security…
               ii.    Click the Security tab
               iii.    Click "Add…"
               iv.    Type yourMachineName\ASPNET in the bottom textbox and click "OK".
               v.    Make sure the Read & Execute, List Folder Contents and Read boxes are checked. Make sure  permissions are propagated to all subfolders.  Click "OK"
    b.    Reset IIS
5. Restart Visual Studio, update your project references to use the new version of Oracle.DataAccess.dll, clean and rebuild your solution