Thanks for the advice.
Yes, I used Win 7 advisor and it reports a custom install.
Regarding drivers, it refer me back to Dell website.
At the Dell website, it has only vista drivers, no win 7 drivers. Yes, its a pretty old laptop but its running well (on XP pro) and previous owner has replaced some parts over the years so its still in pretty good shape.
I think its still good for at least a couple of years more and as I have an OEM win 7 lying around unused, I thought of upgrading it.
Just not sure whats the risk of problems with drivers thereafter so hoping someone here has similar experience.
Dell Inspiron 2330