Older boards like yours, it's SATAI, plus I also looked at the specs already. Not sure how to physically tell but I just look at the spec or the south bridge chipset or google it.
The jumper just set the SATAII to operate with MB that have SATAI connectors. When you buy the SATAII hard drive, the diagram for the jumper is on the hard drive and will tell you how to configure which interface to use. Either no jumper for SATAII or with a jumper to short two pins for SATAI.
4 years is not bad, I would always make good backup of your data daily. Can't really trust hard drives, they have a very low life expectancy. Plus after 2 or 3 years, it would be cheaper to just buy another faster, more capacity hard drive and move your data.