Why won't my Dell Inspiron 1520 laptop let me re-install the OS?

[Schwaan666]

Hi I recently formatted my Dell Inspiron 1520 laptop as I wanted to restore it to it's factory settings as the laptop had gotten extremely slow. So I went though the steps of formatting the HD and re-installing the OS, everything seemed to go smoothly, I didn't get any error messages, but the process didn't work. I've tried it about 5 times now, there must be something I'm doing wrong, but haven't a clue what it could be and I would appreciate some help, thank you.
Hi again, thanks for the replies - I couldn't figure out how to reply to the answers individually so I'm adding some more details in the hope of answering everyone's questions.

@SimplyRed - my OS is windows Vista and it came with the laptop, never been used until today. I formatted all partitions before installing manually, I did that for the first two tries and than decided to delete the partitions and make new partitions and that didn't seem to make a difference. I didn't alter anything in my BIOS - the laptop booted from the CD everytime so there was no issues there.

@CommonSense - what I mean by did not work is that everytime the installation process would stop on the 'Installing windows' screen and go no further - the laptop boots from the OS disc and than I start the process of installation, the first time it comes on the installing windows screen it gets to the end of the steps and than the laptop restarts - than a screen comes up with the caption a