replacement laptop hdd

I've obtained two used laptops, an Advent 7086 and an Acer 422DLC. The advent is a non-runner as it's been dropped at some time but I originally bought it for spares to repair an ECS321 which my wife's now using. I know the hdd from this is good as I've run it on the 321 and it boots into XP no trouble.
The Acer I got from someone who was trying to reload his OS and getting nowhere, and I've verified that the hdd is shot.
I'm trying to fit get the good hdd to run in the Acer but can't boot it. Neither will it boot in my desktop (using a 2.5/3.5 adaptor) and I suspect that I need to procure some drivers to suit it's new host machine - is that correct? Any advice would be appreciated.

Unless you tell us exactly at which point boot fails, what you see on screen, and the details of any error message then there is little we can do to advise

However as a couple of general points
1) buying second hand laptops is usually a waste of money. They're usually for sale because they are faulty
2) Acer laptops are not exactly the most reliable brand. They have more than their share of motherboard failures (or at least the older models did). Buying a second-hand Acer is a likely way of blowing your money away

In this case, what do you intend to do with it
256GB RAM, an old Celeron CPU, the hard drive you are trying to fit is a 40GB IDE unit. It doesn't have the power to run Windows XP, let alone a modern operating system. Windows Me or 2000 would run on it OK. Nothing newer
Give up before you waste more money

Many thanks for your comments Jon. I agree that they are old machines but must point out that both were originally supplied with XP Home installed and have COA to that effect. As the intended use is only e-mail and general surfing it is quite adequate - as I already stated I got the Advent as a source of spares for a 321 which my wife is now using for exactly the tasks outlined above. As I only paid £5 for the two machines I felt it was a fair deal considering that you can pay that amount for a replacement key top or a latch on the internet!

Hi Ray, if you have an installation CD for XP you can take the option to "Repair" the installation from the on-screen menu (at the second time of asking; not the first!). This often fixes boot problems like yours.

Ray
like many machines of the time, they were supplied without sufficient RAM. The likes of Dell bullied Microsoft into dropping the minimum specs - and got it wrong. Since then the XP operating system has got bigger and more bloated, resulting in machines that could cope then, no longer can
I appreciate your point about the cost, but to be honest even at five quid I don't think they're worth the effort.
As for the hard drive issue.....Advent used to "tattoo" some of their laptop drives, so did Acer which could well stop them booting in other machines without being reformatted and reinstalled.....not sure if thats the case here. More likely the drive or PC is knackered (despite your comments to the contrary)