I want to buy a HardDrive.....but which one?

Hi,

I currently have a 20g hard drive on my computer. It's 95% full so I want to purchase a hard drive with good capacity.

Basically I have 2 questions.

1) Would my computer be able to handle a larger hard drive such as a 200g? For example could it handle the potential of storing so much data.

My computer is a Dell Dimension, I run Windows XP, with Intel Pentium III processo, 996 MHz and 256mb or RAM.

2) I think it would be easier to give you the links of the hard drives for sale.....the prices are quite resonable (they are in EURO)
http://www.komplett.ie/k/kc.asp?bn=10088 (website called Komplett)
http://www.marx-computers.com/cgi-bin/store/commerce.cgi (website called Marx Computers) both from Dublin.

Any advice would be most appreciated as I always seem to make bad impulsive decisions :-)