As a newbie to Linux, it's worth choosing a distribution which will help to smooth out the learning curve as much as possible. Current distributions of Red Hat include a graphical installation environment, with a high degree of plug and play self-configuration and reasonably clear explanations of the decisions required to get up and running.
An early decision is how to carve up the hard disk into the appropriate partitions.
Unlike Microsoft Windows, Linux requires a separate swap partition for memory as well as the main EXT2 partition containing the operating system itself. These two partitions may be additional to existing Primary Paritions (PP) if a dual-boot system is required.
MS Windows and MS-DOS require only one partition and use a swap file to manage memory, rather than the separate memory swap partition of Linux.
In such a case, create the first Windows PP of required size and install Windows first. The rest of the hard disk can be left as free space, to be configured with Disk Druid (an improved fdisk utility) during the Red Hat installation. Linux will pick up the existing Windows partition and will install a dual boot menu as long as the Windows PP is selected as the partition to contain the Linux MBR (Master Boot Record).
Manually partitioning with Disk Druid is reasonably straightforward. I usually create a 128MB partition first, defined as 'Linux Swap' and then create the 'root' (represented in Unix as the forward slash / ) partition and tell the Druid to use the rest of the remaining disk space. Depending on what features are installed, roughly 900 MB are needed as a minimum partition size.