I'd take it apart and reseat the RAM and CPU card; this is a common issue with 1x0 Powerbooks (some guides I recall reading in the past referred to putting a small shim on the CPU card so it makes better contact. While you're there, check the hard disk ribbon for any damage.

Then I'd remove the battery and leave it be for a day or so. Dead batteries in infrequently-used 1x0 Powerbooks cause the system to not turn on at all, or boot erratically (video corruption, HD doesn't spin up properly). Once the system is hopefully booting normally, you can put the battery in while it's turned on - this will usually result in the Powerbook turning off. But, persevere with this, and generally the Powerbook will work with the battery installed.

Regarding the HD, again if not used a great deal stiction can take place - a firm "spank" on the right hand rest usually sorts this naughty boy out

JB