Windows freezing while downloading….

When I download programs on my PC the whole system locks up after about 15-20 minutes. It’s usually any program not just one specific one ie download manager, windows downloader or steam downloader. I presume theres some sort of memory leak going on but how can I solve it.

Im using Windows XP, E6750 intel, 4gig RAM, geforce 8600gt and sata HDD and DVD.