Once you remove the DRM, then for:
1) .epub to .imp, see this post
2) .pdb (ereader) to .imp, first convert the .pdb to .html as described here
, then use eBook Publisher to convert that .html to .imp as described here
. It's a two-step process and may need you to tweak it a bit to make it work.
If you had a unencrypted .pdb (PalmDoc) or .prc/.mobi (Mobipocket) ebooks, then my Mobi2IMP
would handle the conversion to .imp. Also, lit2sb
does an amazing job converting unencrypted .lit to .imp!