Changing drive path for automatic downloads??

I hope someone can help. I'm running Windows XP Home Edition. Currently my system automatically downloads to my D: drive (only has about 5G memory), which is nearly full. My C: drive has 80G memory. When downloading something, the system automatically saves it to the D: drive, unless I'm given a choice to direct the download to my C: drive, then of course I don't have a problem. However how can I get the system to recognize the C: drive as the main drive and automatically download to the C: drive?? Please help!?!? Thanks!

Thanks for the reply! Fortunately, I was able to handle it. Spent all this time, went into the registry and changed the download settings for Internet Explorer. And I realized...I use Firefox! Duh...in one of the first tabs in it's settings there's a way to define your download directory, which took 5 seconds!! Oh well, at least I learned some stuff. Thanks again for your reply.