Hi,
I have an IBM Thinkpad laptop that requires an AC adapter with 16V and 3.36A. Can I use an IBM Thinkpad AC adapter with 16V and 4.5A rating? My understanding is that the 4.5A on the adapter means it is capable of supplying UPTO 4.5A, not 4.5 fixed. Am i wrong? Is it going to damage my laptop? Thanks in advance.

It is my understanding that just about ANY thinkpad power supply will operate just about ANY Thinkpad, except some of the earlier models had the strange "D" or trapezoid shaped 4 pin connector. So far as I know, all later Thinkpads had the same round connector.

This question of amperage comes up often. As long as the power supply is rated for "enough" amperage, you are ok. Think of it like the power outlets in your home. You may have one outlet with a 20A breaker, but yet you can still plug a little bitty cell charger in there that may only draw 1/2 amp.

same thing on your car battery. A GOOD car battery can supply thousands of amps for a very short period, but yet you can hook a small map light up that only draws 1/4, 1/2 amp, whatever.

I think your power supply will do just fine.

"My understanding is that the 4.5A on the adapter means it is capable of supplying UPTO 4.5A, not 4.5 fixed."

A short answer is 'yes'.