I just got a cable modem and nic card.
Now whenever I download big files like over 50mb's, half way throught the download my pc totally freezes! Mouse cursor wont move and ctrl+alt+delete does nothing! I can leave my pc on all day and no problems! I can play counter-strike for 4 hours straight and no problems at all! Then i dl a files and then bam freezes! I can surf the web just fine. Someone have this problem or think they might know whats going on here. I know its not a IRQ conflict with my nic. COuld it be a bad network card? Its a realtek. My ping though is really low like 15ms.
Win98
DUron 1.1ghz
256mb ram

Wtf is going on!!?! HELP! I called at&t and they didnt noe jack shjjt. They told me to clear temp folder. And clear internet files.. Did that b4 they told meee. Help :)

taking a guess here If I may. I am assuming the temp folder you cleared was the temp internet folder.
You may want to examine your swap file (size and fragmentation issues).
Maybe even try removing the software that was installed with the cable modem. Like If your are using rogers@home then uninstall thier browser and try with a regular copy of Ie or what ever you use. I have seen many different problems caused by 3rd party browser skins/plugings like what @home uses.
In many cases (like mine) I have never used my Isp's software and have never had any problems with connection or like you discribe.
hope this helps :)

Do you have a limit on your temporary internet file folder size? Have you tried turning of the task scheduler when you download? Just a few things I could think of.

My temporary internet files limit is at 1.5gb. Yea i disabled the task sche. a long time ago. I use at&t broadband. If I uuninstal their browser i might have problems connecting? Actually it i dont use it at all.