I have bought a cheap BB from eBay to see if it would be of use, before upgrading to a current model. It has no SIM but is allegedly unlocked. Can I use it like a PDA until I get an O2 SIM and does it have to have a SIM inserted to connect to my laptop?

Yes to first question. No to second.

Having ascertained I can use it, I now can't connect. I am connecting to a laptop that has no serial port and am using a Serial/USB converter. I've tried detecting via USB and the two COMs ports showing but keep getting Handheld Not Found warning. When trying via COM ports I have made sure that the Enable Serial to USB connection box is ticked. Any other ideas?

Do you have the desktop manager software installed? (just checking) Its probally the hub you are using it needs to most likely be a direct connection. I have read in this forums about people having to disconnect the usb hub.

Yes, I have the Desktop Manager installed. That's what is telling me there's no Hnadheld connected. I'll try without the hub now.

It's now looking for Software for the new USB device. Any idea where I can download USB device s/ware for the cradle/BB?

sounds like you need the handheldmanager too get the whole package from blackberry.com