I wish to purchase Lightroom 5 at a discounted price and the upgrade version is attractive. I have an OEM version of Photoshop CS3 which I bought online downloaded from a reseller. Is this OEM version accepted as eligible for the upgrade version?
No. You upgrade from Lightroom version to Lightroom version, not Photoshop to Lightroom.
Thank you, I will decide whether to upgrade Photoshop to a higher version or buy a OEM download version of Lightroom 5.
As an alternative to the OEM route, the Lightroom+Photoshop bundle deal at $10 per month is hard to beat assuming you are not opposed to software as a subscription.