Nowadays, a 'need for speed' seems to be the general theme when buying PC systems, though frankly, the older style systems of 3 - 4 years ago are more than adequate for everyday needs.
In fact if you want to use several computers in a network your server needs to have Windows XP or Windows Server as its operating system for most database files to work properly. If, for example, you do your home accounts and possibly write the odd letter to your bank manager, there's no way you're ever going to fill even a 60Gb hard disk, which would comfortably store the entire works of both Shakespeare and Dickens, with space to spare.

As for processing power , did you know that man landed on the moon using less processing power than is provided by the old 486?

The question, therefore, is 'For what purpose do you need the PC?'. If it's simply for running your practice software, writing Word documents, surfing the internet or making basic calculations, then you'll be wasting money buying a system capable of launching the space shuttle. You simply don't need 360Gb of storage space and an AMD Thunderbird 5000Mhz to perform these functions, though the salesperson might beg to differ

For everyday purposes, you could do well with the following spec:
1000Mhz CPU
80GB hard disk
512Mb of RAM
any graphics card.
If you keep an eye on the second hand columns, there's no reason why you should pay more than £220-00 for such a system.

Another snippet of advice:
don't let the salesperson talk you into buying an advanced system for internet purposes - all you need is:
a basic system;
a built-in modem;
internet browser software such as Internet Explorer
software for setting up an account with an Internet Service Provider;
Most of these are provided with new systems anyway (and easily arranged if you're buying second hand).

Some general buying tips:

*For word processing and browsing the internet, a 400MHz PC with 64Mb of RAM, 4Gb Hard drive, and any display adapter will suffice.

*For playing games, a 1000MHz processor, 1024Mb of RAM, 120Gb Hard drive, and a 124Mb AGP graphics card should be your minimum specification. Most new machines have at least this specification and many a lot better.

*If possible, check if there are any free slots on the mainboard to add memory.

*Upgrading the graphics card at a later date will require an AGP slot.

*If you already have a PC, take a look inside to see if there are any parts that can be re-used. Your sound card, case, power supply, monitor, keyboard, mouse, CD-ROM drive, floppy drive, and display adapter can possibly all be saved. If you know how, just buy the parts you need.

*It's often worth buying a system that's just off of the top specification. E.g. If Intel have just released a 5000MHz dual core processor, look at the prices of 4000MHz systems. There is little real world performance difference, and often a considerable difference in price.

*RAM is inexpensive. Don't pay an extra £100 for a system with 1000Mb more of RAM because it's a simple operation to buy more RAM afterwards and fit it yourself.

*If possible, speak to the vendor and try to get some software bundled in.

*Consider the operating system. Windows XP Home or Vista Home is ideal for home or small business users. Windows NT is very stable, but less compatible with games and aming hardware, making it the choice of businesses. Linux is for advanced users and people comfortable with UNIX.