There use to be a pinned posting for a Windows 7 U3 upgrade but I don’t see it anymore.
Some versions of Win 7 support running a version of Win XP on them for compatibility with older apps and maybe devices. Maybe you can try that?
Here’s that upgrade posting: http://forums.sandisk.com/t5/Cruzers-with-U3/U3-Windows-7-update-now-available/m-p/195046/highlight/true#M5019