Which pc based diagnostic tool do I buy

[mre15]

I am looking to get a usb diagnostic tool, can anyone recommend a good one.
I have looked about but there are som many different ones to choose from.

Cheers.

[AlexB]

ELM327 v1.3a or v1.4 (the higher versions do not exist at the moment, but somehow still advertised). I use the one where the electronics block is combined with the OBD2 connector in the same body. It comes with ScanMaster software on a CD.

Please note, any EOBD tools are for the engine only. Steering, airbags, ABS, immobiliser, etc. are only covered in the special manufacturer's tool (Clip for Renault).