The thing is, I can boot it back up, and leave it run for another half hour.. But the battery reads 0%
Are there any ways to recondition the battery so that I can get a proper reading? Or should I just suck it up and get anew battery for $20 on amazon?
This is a common symptom on batteries (esp. Sanyo, according to my experience). The battery degrades, but the gauge degrades even more, and consistently reports the battery being at 0% when there is actually quite a bit juice left. With two batteries in similar condition, I found that I could improve the accuracy a bit by recalibrating (a couple of full discharge-charge cycles), but not too much.
If it's important to you to get the last bit of juice out of the battery, disable the automatic hibernation feature by Windows. If it's important to you to not accidentally lose data when the computer turns off, then it's time for a new battery. In any case, it's probably a good idea, since according to your times the battery is very worn and lasts only for 45 minutes.
Additionally, I might have to backgrade to windows xp, because the function keys don't do what they aught to.. For example, there is no way to turn off my wlan
This is a matter of installing the correct software (hotkey utility + maybe wlan driver from Lenovo).