I have a Nokia 8800 which I bought in Europe and requires so many different adaptors to charge. I have an US adaptor which says that its Output DC is 4.5v max 9.5v. Can I charge my phone that is 3.7v with a 4.5v without harming it? Or should I get an adaptor that has less of an output voltage? Confused please help. Thank you

Too much voltage will fry it, I would suggest getting a new charger or a voltage adaptor.

4.5 volts is acceptable for charging a 3.7 battery- most 3.7's get charged using 5 volts

How about 5.5 V? I'm charging Motorola Milestone therefore there could be some adapter or resistors between.