Some resources and different ways of having Windows and Linux or FreeBSD on the same machine:
1) VMware. Allows you to have multiple operating systems booted up *at the same time*. No rebooting to switch from one to the other. Cost around $300
2) System Comander. Software that helps you to multiboot several operating systems on one box. Cost around $60 or so. This is really helpful if you are limited to one hard drive. It also allows you to resize existing Windows partitions. This means if you have Windows taking up your entire "C" drive, you can reduce the space Windows takes up to make room for installing Linux. Keep in mind there ARE versions of Linux you can install within a Windows partition. I don't recall the distro though. Maybe check out distrowatch dot com or linuxiso dot org -- or Google, of course!
Of course, it would be prudent to back up your current Windows installation with Norton Ghost or some similar "image copy" program before you go resizing your current windows partition!
3) Hard drive selector. These are physical devices which allow you to switch from one hard drive to another. So if you don't want to mess with your current hard drive having Windows, you can install a hard drive selector (and a second hard drive you install Linux upon of course) and then switch between hard drives easily. Some models let you lock out the hard drive not being used, so you can't mess up the hard drive you're not using.
Two I'm familiar with are the NickLock and the TRIOS. Here's a link to a pic of the NickLock at tigerdirect dot com; cost $20 and fits into a 3 1/2 inch bay:
and the ROMTEC TRIOS website is here:
There are two model TRIOSs. Both models allow you to switch between three hard drives. The first model fits into a 5 and 1/4 inch drive bay. You really need to worry about how many open 5 and 1/4 inch drive bays you have with that model. I have a Lian-Li PC-70 case, so it's no problem here, but YMMV.
In many computer cases you will find it imposible to mount the drives and run the supplied cables that come with the TRIOS I. You'll need to buy longer IDE drive cables from them to reach between the TRIOS I and your mounted drives in some cases (no pun intended). The first model/version TRIOS I cost around $50.
The TRIOS II, or second model is a $75 PCI card and cables setup that also permits you to select beween three hard drives. However, unlike with the TRIOS I where one drive is active and the others locked out, either one or two of the hard drives can be "active". Also, with the TRIOS I, all three hard drives spin up. With the TRIOS II, only the active hard drives spin up -- the other one(s) don't get power to them. This is all IIRC, so please see the website for latest details if you are interested. I've not had this model, but it looks like you would have less trouble running the supplied IDE cables between the PCI card and hard drives mounted in internal 3 1/2 inch drive bays as is more typical with most computer case configurations.
4) The Multi-Boot Configuration Handbook. Tells just about everything you would want to know about multi booting operating systems. Covers most all the methods -- especially those done with software/boot selectors.
5) Installing a second hard drive and manually installing Linux upon it and selecting install options that tell the Linux installer to put Linux on the second hard drive -- and not to mess with the first hard drive having Windows on it -- except for installing a boot manager, i.e. GRUB or Lilo, so you can select which OS to boot into during power up. You can specify all this during the RedHat Linux installation. Some other popular installations likely allow this too. Doing a Linux install is pretty easy for most folks nowdays. Most popular current distributions like Red Hat, Suse and Mandrake detect and work fine with mot hardware. You may have a problem of course -- winmodems come to mind -- but it takes less than an hour to install Linux these days on most computers. So why not just try and see it it works ok before worrying about it too much?
6) Google up on GRUB, multi booting operating systems et all and knock yourself (and hopefully not your Windows installation) out!
Hope the above helps!