I just installed W7 and found that I no longer have a thumbnail image of RAW files. Just a icon. There is a program, Fast Picture Viewer, that solves the problem by providing the Codex for most RAW files. Its a bit slow opening a big folder with many large raw files but not unbearable. One version is called "donationware" where they suggest that if you end up keeping the pgm that you provide a reasonable donation.
BTW, I downloaded the Canon Codex that was supposed to solve the problem for the Canon files but it did not.
Thanks Joe S