Ok I have done some further testing and here's my results:
1) When physically plugged in, it still hangs on occasion but what I've since realised is that all you have to do is wait about 5-10 seconds and the "(not responding)" goes away. This never went away on my other PC no matter how long I waited. So, it seems to be pretty good so far. It's still not ideal that the "(not responding)" still happens 50% of the time but at least my success rate is way higher now. Out of about 3-4 times I used it, it never once hung completely. On my other PC it hung completely 9/10 times...you can imagine how insane I went trying to setup my games!
2) In regards to wireless connectivity, I uninstalled the Targus provided bluetooth drivers as you suggested and let the default windows one auto-install, then rebooted. After several attempts, it finally worked! However out of the 4-5 other times I tried to get it to work it only picked it up one other time. And when it does work, it always searches for ages before it is found whereas all my other gadgets come up very quickly. Question - when I press the P button on the XIM, how long does it stay in discovery mode before "timing out"? Also I've tried pressing the P button both before and after Windows goes into BT search mode - neither appeared to be more or less successful but which one do you recommend? In the mean time I've also ordered another BT adapter off eBay to see if it's the Targus one that's acting up. That iPhone app can't come soon enough!