EasyBCD didn't cause any of your problems
You won't have damaged W7 with the drivers. It's not going to allow a non-suitable driver to replace the right one. You've just got some unwanted extra files which will sit unused.
You chose to install an old OS with a newer one.
Old OSs by definition don't know about newer ones, and are therefore not compatible with them.
You shouldn't let old see new for that reason.
It's nothing to do with the app you used to configure the BCD, it's a fundamental (but managable) clash of generations, and sloppy programming practices by some app writers.
Just follow the advice at the end of my last post and both systems will be fine.
When both systems are running as required, with XP unable to see any of the contents of C: in Explorer, make sure you set system restore on each OS to be on for itself, and off for the other OS and any shared partition. If you install apps (like I do) to
separate partitions, you need system restore turned on for the apps of each OS. For that reason, the app partition cannot be shared, you'll need one on each OS, and XP mustn't see Vista's.
It doesn't matter that XP isn't C:. Mine has been D: for years.