The "dd" command can be a very dangerous tool if you don't know how to use it. I personally would not.
Correct me if I am wrong, but I would guess that the Windows install disk was made to be able to install to an untouched (ie: unpartitioned) disk. In which case you would simply need to delete all the old linux partitions on the drive before installing to it.
If that is not the case, then you can use various tools to make the drive one big ntfs partition before you install.
Available tools for the job would be any number of partitioners you can buy (Partition Magic, Acronis Partition Expert, etc...), or there is also a set of free linux tools, for which I would recommend downloading the KNOPPIX live cd
The knoppix live cd has a program on it called QtParted, which will be able to do everything you are needing and is very similar in look/usability to the proprietary partitioners I listed above. Simply boot it, find qtparted, and go to work. Should be quick and easy.