Need to replace netbook power cord

Hello, I have a very elementary question to ask: the power cord to my Acer Notebook no longer works so I took it to Best Buy thinking it'd give me all I needed to know to find a replacement. It's got a 19v power supply…but I don't see any mention of wattage anywhere. Cords available at Best Buy were the Rocketfish Universal Netbook charger which is a "40 W with variable output of 12-19v" power cord or another brand which was a "90W and 19.5 v output". The tips on both are the correct tips but I have no idea what wattage I'm supposed to have. I came home with the Rocketfish and it's plugged into my notebook and seems to work fine but I wanted to make sure I'm not harming anything… The Rocketfish box says "Not compatible with 65W, 90W, or 120W laptops" which is what concerns me. How do I find what my notebook wattage is? It doesn't seem to be listed on the bottom of the computer and nothing is mentioned in the user's guide. My model is an Acer Aspire One notebook KAV10. Thanks, MM

Hi MM,
The power supply that you bought has suffcient wattage for your Acer KAV10.
The most common PSU for your Acer KAV10 has a 30 watt output on19v so your wattage at 40 should be just fine….
Note 1the voltage must be correct when replacing a PSU so 19v is exactly what you want, but make sure that you cannot accidentally switch it to more than 19v whilst in use as that could "blow" the computer…and damage it beyond economic repair.The tolerance is very small on voltage so make sure its exact.
Note 2 the wattage has to be sufficient to drive the computer….. the wattage required means you need 30w or more…. so your 40w is fine
Hope this helps and puts your mind at rest.
Regards
paws

Thanks, Paws, for putting my mind to rest. There is no switch on the PSU and it says "19v". I was kind of surprised that the original PSU went bad…I didn't realize they could become inoperable. Guess I'll be more delicate with this new one