There are so many ways to modify the Start button label, from using hexadecimal editor to using 3rd party tweak applications. But I choose this way because I think this ways is simplest one.

1. This trick will need an application that calls Resource Hacker. Download Resource Hacker in there. The downloaded file is in a Zip format, so unzip it first. I suggest unzipping it on a folder at root folder, giving the folder name: ResHack (you can put it in whatever you like folder).
   
2. Open it by double click the ResHacker.exe file.
3. Open explorer.exe file inside your Windows installation folder (usually in C:\Windows).
   
4. At left panel, navigate to String Table -> 37 -> 1033 key.
   
5. At right panel, find line 578, “start”.
   
6. Replace it with your own label but the new string doesn’t too long.
   
7. Then click Compile Script button.
   
8. Save it in your Windows installation folder and give it file name with your own name but don’t explorer.exe. I give it name: oo_explorer.exe.
   
9. Now, you have a modified explorer.exe file. The next step is pointing Shell registry value to your modified file.
10. Open Registry Editor by click Start -> Run, enter regedit in box and then press Enter.
    
11. Navigate to \HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon key and then Find Shell value.
    
12. Shell value has default value data: explorer.exe, just replaces it with your modified explorer.exe file (in my case I replace it with oo_explorer.exe). To modify its value data, double click Shell value then replace its value data in box and then click OK button.
    
13. Close Registry Editor and restart your computer.
14. If you did it right, your Start button label has been changed.
    

I tried this trick on Windows XP SP 2, if you’re using others version, you can find its key on step 4 in other path. Just explorer it one by one until you find “start” string at right panel.
(article no:0113)

To hide it, we’ll play again with registry.
1. To modify registry value, open Registry Editor by click Start –> Run, enter regedit in box and press Enter.

2. Navigate to HKEY_CURRENT_MACHINE / Software / Microsoft / Windows / CurrentVersion / Policies / NonEnum path.

3. In NonEnum key, create a new DWORD value. To create it, right click on empty space on right panel, and then choose New -> DWORD value menu.

4. Replace the original value to {20D04FE0-3AEA-1069-A2D8-08002B30309D} and then press Enter to save it.

5. By default, it has value 0. To make this trick works, change it to 1 by double click the {20D04FE0-3AEA-1069-A2D8-08002B30309D} value, and replace the 0 to 1 in box and then press Enter or click OK button.

6. Close Registry Editor and restart your computer.

7. Now, your My Computer has been disappeared from Start Menu and Desktop.

To show My Computer back, just delete {20D04FE0-3AEA-1069-A2D8-08002B30309D} value or change its value to 0.