what do i need for my PC to play DVDs?

[apache]

If I have a RW/CD player will it play DVDs?

[Plotloss]

DVD-RW/CD-RW or CDRW/DVD Combo Drive?

The only additional thing you will need is a DVD Codec pack.

[ThePassenger]

You will need some software. Windows can't play DVD's on its own.
OS X can (just pop in a disk).

You could buy something like PowerDVD or simply download (for free) Video Lan Client (aka VLC) it'll play DVD's DivX/XviD stuff without needing anything else.

[apache]

god knows, I think it's only got a CD/RW

[ThePassenger]

apache said:

god knows, I think it's only got a CD/RW

In that case, no. It won't play DVD's. You will need a DVD drive, same as your hi-fi's CD player can't do audio DVD's, sorry.