The last month I've been getting constant freezes after my computer has been booted up for about 5-10mins.
This forces me to manually restart it. It has also been running rather sluggish at times for the past 2 months.
Every third freeze or so I'll get the Blue Screen Error Msg "One of your disk needs to be checked for consistency".
I originally built this computer back in 2007 as my second home build. I've replaced the graphics card, power supply and CPU. Also I've reformatted the hard drive twice.
My question is are these symptoms that my hard drive is about to go?
I've dealt with multiple hard drive failures in the past on various machines. Linux is usually pretty good at running even if the system drive is forcibly unmounted or rendered unreadable (although some services are not tolerant of this). Windows on the other hand will usually attempt a graceful failure (the BSOD message that you're getting) when it cannot read or write from the system drive.
In all likelihood the drive has already been damaged beyond full recovery so what you need to do ASAP is get PartedMagic and burn it to a CD (use another computer to do this if you can). Parted magic is a linux LiveCD that is very useful for doing system maintenance and recovery. Use it to mount the system disk and backup whatever crucial information that you want kept to an external storage device. If you do not need to back anything up you can skip this step.
Next, you need to buy a new hard drive. I don't know what your budget is but the Western Digital Caviar Black series offers the best performance and capacity in the 7200 RPM category. There are a handful of 10,000 RPM consumer drives available (WD Velociraptor) but these are noisy,expensive, and easily outclassed by SSDs