According to the power meter on my Compaq Presario laptop, the battery now only charges up to 99% whereupon the battery indicator light starts flashing. This has been happening for a fortnight. Previously the battery charged to 100% whereupon the battery indicator light was extinguished.

Does this mean that I should now replace the battery (which, with the laptop, is nearly 2 years old)?

It shows reduced battery performance. Still charging to 99% is OK. Mine currently only charges to 74% and I've been too lazy to replace it.

When it is charged to 99% and you put your mouse over the battery icon in the taskbar, does it say something like: "99% available (plugged in, not charging) Consider replacing your battery." ?

If you don't have the battery icon in your taskbar you can add it using Control Panel.

Turn off the computer, remove the battery and reseat it.

Possibly a dirty contact?

How long with the computer run on battery alone?

That is the best indicator of the state of the battery.

I have had problems on a number of laptops with the internal

charging circuit, and an expensive replacement battery did not help at all.