While nice and in many ways incredible that something this old is still usable, it's a 19 year old computer. Seriously, it's 19 years old.
Scrap it.
You can get an adapter for $10, an OEM for $20. Plus a battery ($20), and it probably WILL need ram. Max is 2gb (of DDR1), so $8 on Ebay. You're now into this for $40-$50.
On the other hand, you can buy a used/functional T420 (2nd gen Core I series) with 4gb ram for about $50-$60 with shipping on Ebay, many are Best Offer, so you can probably get it closer to $50 or less. Keep in mind, even the T420 is 12 years old at this point.
Besides it's age and specs, there's another issue looming in the background for older tech like this.
Many Linux distros are dropping 32bit support (MS was close and still could drop it from Win10), so even if it is reviveable, technology is (FINALLY) marching on. This laptop also has the disadvantage in that it uses a graphics chipset that isn't well supported by Win7 or later. You could sometimes force a very specific Win XP driver to work, but often you were stuck at 800x600, rather than the default 1024x768, which was already bad enough
Bottom line, don't mess with anything pre DDR3 unless you have a genuine reason. Yes, DDR2 usually supported 64bit, but DDR2 has it's own issues, besides it's age. If you want to actually use it, stick to DDR3 stuff. It's plentiful and cheap.
