How to Prevent access from a certain folder?

I want to lock a certain folder and unlock it using a password, any ideeas ?

PS I am a delphi coder!

There exist several approaches:

1. block access to the folder to any application until it's unlocked. The files remain unchanged.
2. encrypt all files in the folder and decrypt them on-the-fly.
3. move the files to encrypted storage and mount this storage as a virtual folder.

The first approach is flawed as it lets the user reboot the system in safe mode or just take the HDD to other computer and gain access to the folder.

Second approach is possible using file system filter driver. You can write your own or you can use our CallbackFilter product (which includes Encrypt sample for this particular purpose).

Third approach is also possible using our products. You can mount a virtual storage as a disk or as a folder on NTFS disk using Callback File System (see VMounter sample).

There exists also Pismo File Mount product on the market and it would work for you out of the box if it had Delphi API. That product mounts a container as a folder on the disk using FS Filter driver. Personally I am not fond of this approach, though -- FS filter drivers are trickier than file system drivers and more prone to conflicts with third-party filters.