Dell Dimension 4600 hard drive/what to get

Hi,

My old hard drive on my Dell Dimension 4600 (2004 512mb 400mhz Pentium 4 Processor 2.8GHz)  is about to die and I would like to replace it with a 250gb, the old one is a 80gb...I will be using a hard drive enclosure to move/save files.   Looking to spend under $100.

Would like to know what you guys recommend on what to get (specs), any info help would be greatly appreciated

Thanks

Bil