Hey there, overclockers is a good website for computer component purchases, however do check out ebuyer.com and gladiatorcomputers.com because you may find the same product cheaper. for the harddrive it depends on what you want from it. if your looking for a high quality, reliable, superfast drive then id go with the western digital raptor series as they feature 10,000rpm opposed to the more common 7200, links shown here:
36.7gb
http://www.ebuyer.com/customer/produ...duct_uid=50948

74gb
http://www.ebuyer.com/customer/produ...duct_uid=55454

Now if you want something that is reliable, cheap and not so fast, at the more common speed of 7200rpm i recommend seagate as they have been proved to be extremely reliable harddrives. Links here:

http://www.ebuyer.com/customer/produ...ubcat_uid=1090

for external harddrives Freecom own that range, fast, reliable but a bit pricey link here:

http://www.ebuyer.com/customer/produ...duct_uid=97954

However if you want something a bit cheaper seagate do a 400gb for a considerable amount less

http://www.ebuyer.com/customer/produ...duct_uid=95637

Hope this helps