Welcome to the forum!!
I looked up the two 2GB 5450's that are listed on Newegg:
HIS H545HR2G Radeon HD 5450 2GB
PowerColor Go! Green AX5450 2GBK3-SH Radeon HD 5450 2GB
The HIS states a minimum of a 400W PSU, and the PowerColor states 350W. You will need to upgrade your PSU even if you were going to only use it in 2D mode I would be willing to bet, but there would be no way that you could power that card with just a 64W PSU.
The review here
states that a system with a reference ATI 5450 uses 150W at idle and 161W at load, stressing the card with Furmark, which is almost a straight 100% usage on the GPU core. Taking into account that they used an i7 965 Extreme, I would say that most of the power draw is from the CPU alone...LOL...way overkill for testing this card out....HAHA....no way that any of the results show that that CPU is limiting the GPU there....LOL.
review on the other hand appears to factor out just what the card would pull for the HIS 5450 running with an i7 920, it states that the card only pulls 5W at idle, 12W at average usage and 13W at load. So that review would make it seem that you should be able to even on the non-green powered HIS, it would be lower with the PowerColor I would imagine.
All that said, your 65W PSU would need to be a top quality unit to ensure that you are getting as much wattage/amperage to your components. Even if that PSU was rated at 80Gold status that would mean that you are only getting roughly 52W of true power to the components, the rest is being lost to heat. I would be willing to bet that your PSU is a generic one so you can count on it supplying even less that 52W to the system. If I were you I would look at getting a different hight-quality, low-power, PSU if you intend on getting a 5450 for it. Remember, the PSU is the most important
component in any computer.
The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates.