Hello, is there any reliable tool which can help save a website's folders and files on a pc for offline use? I've tried HTTrack but it does not save all the folders for the website i want to have offline...

If it is a site you own, you should have the development oroginal copy on your pc.
If it is a site you are taking over to edit, use ftp to download the entire site.

If it is a site you wish to examine that belongs to someone else, HTTrack is your best bet, but if it does belong to someone else, why do you want a local copy?

in fact the website is for a new client, who has got some problems with the existing hosting service provider, and the latter has cancelled the client's ftp login account. the host provider is also the one who the client had hired previously to create the website. however the client wants the same website to be done again and hosted on a new server, but does not have any copy whatsoever of the site, thus asking us to try get all the files hosted there and move them locally temporarily until he decides the new hosting service to be used.