Here are your options from my experience.....

1. Upgrade your BIOS - this may allow it to recognise larger hard drives than it currently can (older machines have limits on the largest hard drive that they can see). I'd suggest looking on the website of the manufacturer of your machine (or motherboard) and seeing what they say for largest supported hard drive. They should also have information on what BIOS level is needed and how to upgrade it.

2. Get hold of an IDE PCI card - this is a second set of hard drive controllers that plugs in to a PCI slot on your motherboard. You can then plug in drives of any size directly to that without any problems - I was running a fileserver for a while at home on a Pentium 233MMX with a couple of 120GB drives plugged in to that as they weren't recognised by the machine itself.

3. Upgrade your system - you'll likely need a new motherboard, memory and processor as well as the hard drive.

To answer your questions....

A BIOS - Basic Input Output System - it's the software that tells all the various chips in your machine how to talk to each other - how the processor talks to the sound card, the memory, the hard drive etc at the absolutele lowest level - how to boot up, how to read from a hard drive etc.

B Buff Speed - I think he's referring to the fact that hard drives have memory in them so they work faster - if you assume that all the bits that make up a file are organised in one place, and files that are used together are stored together on the hard drive - then it makes sense that if you read the next few files on the hard drive at the same time as the current one then you won't have to go looking for em the next time. To be honest it doesn't make a lot of difference unless you're doing video editing or real intensive stuff like that. Go for the cheaper option if you're using it for storage.

C Anything important - I'd go for the maxtor range - they're normally pretty reliable, also think about partitioning it in to a couple of drive letters and get in the habit of back up all your critical files to there (or even backing up your entire operating system). Otherwise do what we all do - look at the prices, read the reviews and make your decision. Google is your friend in this.

Hope this helps... Spanky