Download free convert 64bit to 32bit windows 7

You can't. You have to re-install the OS.

while installing os for 32 bit, earlier files may be lost or not in c drive

You can. But it's some serious editing and not recommended. (very bad idea)
You'll end up destroying your data most likely anyways. If you have to ask how to do it your not qualified. Back up your data and do a clean install... If your that concerned about keeping your data you should be backing it up anyways.

Can't be done.

A conversion to/from 32-64 bit requires a clean install.

You can export your files and settings using windows easy transfer and then import them back after the clean install.
Apps will have to be reinstalled.

And... you can reuse your original windows activation key which is 32/64 bit independent.
You can borrow any 32 bit dvd to do the job.

Is there a reason why you want 32 bit and not 64 bit?
I have done just such a conversion in order to be able to run a specific 16 bit program, but otherwise, there is not much reason to convert.

Yes backup what you want then reinstall there is no way to convert. Also why are you doing this there is no reason to go back to 32 bit 64 is the way to go.

Thent