Long ago, after few months installing my Win XP, i decided to change my D: format, from FAT32 to ---> NTFS. The main reason why i did that, its because I want a safer security for the driver. Later on, it works perfectly fine. All files cannot be accessed by other users who logged in with another login account. As an administrator, I can manage all the things that i wanted to and change all security settings etc.
To shorten the story, my C: was infected by an unknown virus. The virus does:
1- Changes all folder font type into Windings.
2- Most folders cannot be accessed.
3- Fooling with Bytes display; e.g. the thumbnails says it has 200-400k KB, but when i check its property, the bytes are ZERO
4- Some folders cannot be deleted; since its gone wild.
5- Greatly slowsdown my PC.
6- Can't remember anything else...this happens 3 years ago
D: was not infected at all, and so then I decided to format drive C:, reinstall Win XP and the problem SOLVED entirely. The next thing I experience, was that the security for my drive D:, isn't working. All turns back to normal, just like FAT32 format. I can't manage my security anymore and secure my files in drive D:. Somehow, I decided (stupid me...

) to change the C: FAT32 format to NTFS format. I was then hoping that I could setup my security for my C:, but it was too isn't working. I can't at all manage my security setup as if I'm not a administrator anymore

What happened here?
How can I get back to be admin. again? So that I could setup all my security and so on.