Imaging from two Dell cpus and loosing 1/2 hard drive capacity

I have a dell inspirion e1505 laptop with 50GB hard drive (call it cpu “A”). I bought the system with a dell service contract, so therefore there is a partition in the drive. I am running xp, and have made a complete image of the drive and placed it on an external 500GB drive. I have acronis 9.0 build 3,854.

I also have an older dell inspirion 2200 (call this cpu “B”) that I am trying to create as a working backup. I also have a hitachi 120GB drive as a replacement for the dead drive for cpu “B”.

I have imaged and restored images in the past and it has saved my life.

I took the 120GB driveand connected it to the cpu “A” via usb interface connector. I could see the 120GB drive. I ran acronis on the cpu “A” and had it place the 50GB image on the 120GB drive.

I took the 120GB drive & put it in cpu “B” and I get a pseudo blue screen of death saying “replace the hard drive or hard drive controller”.

I take the 120GB drive out of the cpu “B” and connect it to cpu “A” via the usb port, and presto the original 120GB drive is now only 50GB.

I take the drive back to cpu “B” and I have the original Installation discs, which I procede to run, removing all partitions, and reformatting the disc. It loads windows, but is still only a 50GB drive.

FIRST Question how do I reformat the 120GB drive and get 120GB of space?

SECONDLY Assuming I can drop the 50GB drive image on the 120GB drive (without making it a 50GB drive also), will that image work from the dell inspirion e1505 (cpu “A”), and run on the dell inspirion 2200 (cpu “B”)?

When I bought these computers I purchased a service contracts (drops, spills, …) and dell installs a partition with windows for their remote use. Now that the contracts are out of date, DO I NEED these partitions? What is the advantage of keeping the partitions on my cpus? I am running word / excel / photoshop / and emailing / surfing the web. I sense the partition issue is whats reduced my 120GB down to 50GB. Can you recommend a link or 2 that will educate me as to why I need or don’t need partitions.

I than k you in advance for your help.