In this case, you don't need to bother with uninstalling linux if you are going to repartition the drive anyway. You can run fdisk and delete all the partitions including /swap. Reboot with the Windows cd in the cd-rom drive. When asked, tell it you want to create 2 partitions on the drive. Let it create the one for windows and wait until you install linux to create the linux partitions. When finished seting up windows, boot the linux install cd. If you already installed it once, you should know what to do. The only difference will be setting up the boot loader which can be lilo or grub. Pick either one and have it installed on the master boot record (MBR). You can also pick which OS to boot into by default if one is not picked with a certain amount of time. That amount of time is usually set to 15 seconds but you can change it to whatever you want.
If you do not want to reinstall everything on the linux partitions, you can use a program like "parted" which will let you resize your partitions without destroying the data on them. If you go this way, you'll need to reinstall lilo after installing windows because windows overwrites the MBR.