I have a new generic-brand machine running windows xp, with 2
identical 250MB drives. When I do a hard boot (i.e., power the machine
off, and start it up), both drives appear in Windows. However, when I
do a soft boot (i.e., restart from within windows), one
of the drives (the C drive, which is where windows is stored) appears,
and the computer does not recognize the other drive. I've looked in device
manager etc, and the other drive just isn't appearing at all - i.e.,
there are no obvious conflicts.

I am looking for leads on why this might be occurring and what to do
to solve it. Will give you an extra tip if one of the leads you give me
solves the problem!

I have had cases where the ide cable is actually a bit damaged, it
might be worth trying another. Make sure the master and the slave are
also setup correctly(you have probably checked this already, but I
thought I'd mention it).

If that then fails try taking out your cd/dvd drive and hook up your
harddrive on the 2nd ide channel, so they you will just have 1
harddrive on each channel.  If that works then put your cd/dvd back on
the 2nd channel and try it again.  If this works then at least you
know its not an issue with your power supply.

Hope this helps

Check the bios too.

You might even have a faulty motherboard. I have an Epox motherboard
and I get this, mainly due to poor manufacturing (do not buy epox
boards).

Do as the previous guy suggested, replace the IDE cable (or sata) and
then go into the bios and try and detect the harddrive that way.

usrhlp

yer i had this problem it turned out that a program using the drive
interefered with the registry encoding on windows. I resovled it by
going looking on the microsoft support centre which told me how to
edit the registry encoding. However this maybe a hardware issue, if
you have tampered with anything inside the computer a static shock
could have shorted a circuit. If this is a software issue and you
havn't the time to edit the registry key the easiest way to resolve it
is to re-install windows or to use system restore (this may not work.
Click on the my computer icon then once on the my computer screen
right click select properties a new window will open click on the
hardware tab then click on device manager locate your device here once
you locate your device right click it and select properties if in
currnent status you should get an error codec search for this number
in microsoft support and they should tell you how to deal with it if
the device does not appear in device manager you should click scan
hardware for changes. As i say the easiest option would be to
re-install windows