Generally, if either side of a connection is hard-coded, both sides should be. If one end is hard-coded 10 full, it doesn't send FLP so the other side will be at 10 Mbits/s. If hard-coded full duplex, it also won't send duplex negotiation so the other side will default to half.
If you set both sides to auto/auto, you should negotiate to 100-full, which is the best the 1841 is capable of doing.
You could also be able to set both to 100-full and get the same result. However, hard-coding disables MDI-X negotation so the link won't come up if you're using a crossover cable where you shouldn't be or vice-versa.