.dat files

Can some one please help me.... I have been getting files forwarded to me with the extension .dat and I don't know what it stands for, or how to open these files. What program should I be using??? Or do I need to convert the file first, and if so, how the heck do I do that????:confused:

Notify the sender to send you files in a format you can read, or how to read them, or stop sending stuff.

Dat files are usually associated with anti-virus or files sent wrongly.