CAT5 Ethernet cable

[Paul Lee]

Hello,

I have two computers with different Ethernet cards, DEC tulip & 3com 10BaseT.
When I talk to a vender, they say I need to use cross-over cable since my network
doesn't have hop. But being a newbie, I don't know much about anything.  
I got some cable but it looks like it's not working (maybe setup is fault). 
It says "CAT 5" and has only 4 small wires in inside.
Is it correct cable? Any help will be greatly appreciated.

Thanks,
Paul