Hello,
I'm new here and I don't know much about installing hard drives this would be my first time doing so my question is that I want to replace the my old hard drive which is 40 GB to the 250 GB and I was told by Dell that my computer only has one bay so they said just installed the hard drive leave it at cable select and just install windows XP because it will detect on it's own but I'm confuse because western digital provided their software to use and dell method seem is easy to do so which is the best method to go with what Dell tech told me to do or use the software western digital provided which is data lifeguard tool? Also is it necessary to partition the drive? I rather have the full capacity if that is possible I'm not interested in partitioning. I would appreciate your answers thanks.. :)

It is ESSENTIAL that you partition your hard-drive.
Not doing so create slowing down of start up, and huge problems in case you ever have to reformat your hard-drive.

Do yourself a big favor : create at least two ot three partitions. Install Windows on the C-drive (of 20 GB), and locate all software, photo's, music, and all back-up copies at the D-drive and other drives (any size).

Read all about hard drives, partitioning, and filing systems here : (LINK)

Use NTFS for drive C and Fat32 for drive D.

As for the way to install your hard-drive : just connect the unit (hanging free) to see what happens. That way it is also much easier to copy all data from your old drive to your new drive.

Success !