I have an external harddisk and my friends asked for it. The point is I don't trust in his anti-virus software.

Is there anyway to allow some folders (I prepare hdd space for him) to write-able and all others is read-only ? or is there a software that can do like this ? And it would be great if I can have full access on my computer ONLY (may be with some specific software on my PC) and without having to modify anything.

I don't ask for hdd-encryption since I only want to limit the area of write-able folder (and allow my friend to read through all my data), later I can scan for virus myself only in that area ... scanning entire hdd with 500gb/friend is not fun at all !

Sorry if this doesn't seems like the programming questions. Any help would be appreciate, Thank you.