While I did uncover a service manual at http://tim.id.au/laptops/acer/aspire%205110%205100%203100.pdf

I strongly suggest you try two things and then consider it beyond economical repair and end of life.

1. Replace the CMOS Battery (see service manual.) It's well beyond the years this is expected to last. Figure under 5 dollars. If the machine is not worth 5 dollars, then time to start shopping.

2. The generic reset. Noted at:
http://forums.cnet.com/7726-13974_102-5643855.html

Since this is quite old, even the current #1 250 buck laptop should be cheaper than repair:
http://www.amazon.com/Best-Sellers-Electronics-Laptop-Computers/zgbs/electronics/565108
Bob
Bob