Hi,
Sorry for the delay.
I downloaded Windows with SPI iso (thank so much for the link, in French, or other language, waw!). Download was very long, even on ADLS : 6 hours but worked smootly.
Burning the DVD was a little fussy (for me) but I founded a sotware on Microsoft website wich helped me do a bootable DVD, here's the link
Créer une clé ou un DVD de boot Windows 7 : Windows 7
As I work on my PC, I was a little delayed, but finally I did the "repair install" this morning, and everything is as hoped for.
Eventought it was longer than a clean install (which I did twice before) I really appreciated not to have to remove SPI and Updates, resintall all sofware... and so. It is exactly what I wanted.
By the way, if French readers follow this instructions, in French, repair install option is call "Mise à Niveau" *(upgrade). Weird, but transations often are weird at Microsoft.
I wanted to thank you Britton, for your help, time, support, and specially the link.
Best wishes for 2012!
Marie