I modified the default.aspx of a site definition, renamed it as
about.aspx and put it in the TEMPLATE\LAYOUTS\1033 folder. however
when i opened it in sharepoint
http://Servername/SiteName/_layouts/1033/about.aspx, the "Modify my
shared" page button does not show up. I modified the page so that the
Quicklaunch contains a webpartzone and the rest is just ordinary html.

I tried copying the original default.aspx and paste it in the 1033
folder and accessed it
http://Servername/SiteName/_layouts/1033/default.aspx but the "Modify
Shared Page" button does not exist too. Because of this i cannot add
or modify the contents of the webpart zones.