On boot up system does not find hard drive. it is connected and has ran for the past ten months without any problems.

you are pretty much right it may be a corrupt bios, however before we come to a conclusion try isolating both Seagate Barracuda 7200 rpm 80gig ide hard drive and optical drive only and then see if it at least goes past the bios screen, if yes then the bios is ok and just needs to be resetted to defaults. dont expect it to load windows even if it goes past bios check as hard disk which helps to boot to windows would be removed. also in case if you are using 2 ram slots try connecting only 1 ram chip in 1 slot and then see if it goes past the bios test screen. do reply with results. Good luck.

2000-0142 is an UNREPAIRABLE hard drive failure.
IF you can boot to windows, do so and copy any important data to a CD, DVD or external drive before it completely fails (If system will not boot in normal mode, try safe mode (F8 at boot)
If you cannot boot to windows, then you may be able to get a replacement HDD, install windows and drivers on it, then using a USB HDD adapter, see if you can find your data on the old drive.
Regardless, the only way to fix the computer is to replace the drive, there is no tool that will REPAIR a 200-0142 error on a hard drive, only replacement.

This is a possibility, the T23 is a very old laptop.
Normal 0 Check the BIOS to see if the hard disk is detected, if not open then re-seat the hard drive.
If the BIOS does not detect this hard drive, then the hard drive is probably faulty.
If it was me, I would not waste my time and money trying to get a new hard drive for this ThinkPad.
Disk drive manufacturers do not make small capacity hard drive anymore and the current range of hard drives won't work in your ThinkPad because the BIOS cannot support these hard drives.

it look like harddisk problem is keep going. plug out the disk and try. if it continues and says there is not problem you can say mmotherboard is working well and you have really disk problem

If it is clacking you will need to replace your hard drive.

I’m happy to assist further over the phone at https://www.6ya.com/expert/lou_afa492c634393790

1. Boot to the bios with the HDD connected
2. Turn on all the lock lights on keyboard (SCROLL< CAPS<NUM)
3. Press ALT+E (Wait for Beep)
4. Press ALT+F (Wait for Beep)
5. Press ALT+B to reboot
6. IDE redetect should initialize on boot.
7. HDDs should now be seen

Hiya. Why replace the hard drive? When you say your computer failed to boot - are you sure it wasn't booting? Maybe it did boot but your screen remained blank. It sounds more like a screen problem, quite likely the ribbon connection is loose or it could be damaged. Its a very common problem and tilting the screen moves the ribbon a fraction and it then makes the connection. Try switching on and if the screen is totally blank, no message at all, no flashing cursor then its the screen. If you wanted to be 110% sure, easiest way is to connect laptop to an external screen and test it that way. Hope this is helpful.

Unplug the the dsl & any other device except the keyboard & mouse. Double check the video cable at both ends monitor & PC. Boot up system. If the system starts shut down & connect 1 device. Boot the system. OK? continue to do this. On the dsl there is a reset button. With it unpluged from power use a pen & hold in the reset for about ten seconds. Reconnect the power & reconnect the Rj45 to the PC. Boot system.

Every 4/5 days my laptop fails to boot and I get message "no operating system found"----my drive is only a few months old. However, I have found that if I take out the drive and replace it there will be no problem for a week or ten days. Thus I suspect the problem has something to do with a build up of static. How can I prevent this and save all the hassle?

you need to do a clean install from boot, do you no how??