Macbook Air Hardware Fault Somebody has given me an Apple Macbook Air 1.1 to fix. Unfortunately I have very little experience with Macs.

Symptoms are:

*Computer runs incredibly slow to the extent that I have never seen one so bad. Boot up time is about 15-20 minutes then once logged into the GUI every move is agonisingly slow.

*Battery does not work/charge or is not being recognised

*Fans running super-fast

*When run in verbose mode very many I/O errors on disk0s2 are seen during startup

Things I have tried:


Reset VRAM - no change
Reset SMC - no change except keyboard backlight started working (didn't even realise there was one)
Checked available disk space - About 40GB out of 80GB available
Tried to run in safe mode - no change
Tried running Apple Hardware Tester at startup (by holding down D, also tried Option+D) but cannot seem to access it, possibly because the system is running so slow.
Used disk utility to repair hard disk - no errors/problems found
Checked SMART status of hard disk with Disk Util from the command line - SMART status reported as "verified".


Since there are continuous I/O errors but SMART status returns as OK should I presume that the motherboard is on its way out seeing as other things like battery are also not working? Or could there still be an issue with the hard drive / SSD?
There are only two causes of repeated I/O errors:


A logical failure of the drive due to a corrupted Filesystem 
A physical failure of either the drive or a periphery component (connecting cable). 


S.M.A.R.T. Status is not a reliable indicator for drive failure and is prone to false negatives.  Remember, it’s a firmware function built-in to a drive checking itself. 

Steps:


Boot into recovery mode. Use the repair disk function of Disk Utility to check the boot volume (disk0s2) from your recovery partition. 
Use third party software such as Techtool Pro to scan for bad blocks on your HDD.


Best bet:  

Here is your machine. More than likely, it’s a hardware issue. Specifically, either your drive is failing or the PATA cable is failing. The Apple Hardware Test, even if you were to access, does not test your HDD’s integrity. It would test, however, the input cable to the logic board (the PATA cable) - this is a much cheaper fix.  

Bottom line: You can’t troubleshoot a hardware issue. Backup your data while the drive is still alive. Get a definitive diagnosis from Apple free of charge, and proceed from there.  Once you know exactly what the issue is, decide whether you want to get the HDD/cable replaced by Apple, use a DIY option for a cheaper price, or purchase a new machine entirely. 

BOL.