cannot add 2nd hard drive

my dads computer died so I nicked his hard drive (seagate) 20 gig to use it in my design computer tower along side the maxor drive 40g which is partitioned and is the main drive with the op system on. The computer holds at the end of the command lines and doesnt boot into windows. When I have the drive installed on this computer (my internet) tower the drive is seen as expected and can be formatted and used as without any problems.Although I dont have in depth info is there any rules with adding drives to towers I am missing I have made sure it is slave.Do the positions on the tape make any difference?Thanks
sam

 

Some drives that are masters need a different jumper config when there is a slave than when there isn't. Look on that drive for the guide.

It's also possible that it is using cable-select instead of master/slave. CS cables may have faint markings indicating Drive0 and Drive1 (second drive, or the one that is usually slave), or colored clips.

Make sure that the drive is enabled in BIOS, set to autodetect and not to "None".