ok done!thx thomthom

@pibuz said:

Hi guys!
It may sound repetitive, but I've searched a lot in the forum and I hardly found it at last! So I decided to put it here for a more rapid serach (moderators are free to remove this topic if useless).
This micro-tutorial to explain how to enable the thumbnail preview if it doesn't show up automatically.
It typically happens when you have two sketchup version installed and you uninstall one of them: once uninstalled, your skp files' thumbnails are gone, and you can only see the standard sketchup.exe icon.
A solution is obviously to re-install sketchup (repairing the existing installed version), but most of the times it is more practical to re-enable the thumbnails this way:

Start -> run...
type "cmd" and then press "return"

navigate into your sketchup root directory by typing for example:
"cd C:\program files\google\sketchup 6" and press "return"

now you're in your sketchup6 root folder. Type:
"regsvr32 thumbsup.dll" and press "return".

Done

Hope this can help someone

sorry.may i know where to press 'return' on the keyboard?which key?