Is it the Fn key and F12? for boot menu
have you got one key recovery with the lenovo or is that the partition wiped?
if all is lost...
& you know your net book network card supports pxe then you can reload xp etc using another pc
heres a link to Ryans quite informative web page, 'how to'
i read this the other day i havnt tried it yet but Ryan is a regular poster on computing.net.
There is also a method of installing win7 from usb stick tho the detail is quite deep, you will have to google it if you want win7 back on, cant say it designed for that but some say it works.