How do I download xcode4 from the app store?

Question

It failed a few times during the download but when I restarted it it started again from where it left off. This was good.
However the last time it failed it changed something as when I retry it now it starts from scratch.
It took me about 3 days to almost complete the download so I don't think I am going to successfully download a 4.5gigs XCode file
without any download interruptions.
I have tried copying the pkg in Library/Application Support/App store so that I can get it to start from where it left off. However whatever I try it always seems to go back to 0 bytes when resume is clicked. This is a trick I learnt in Firefox that I used when downloading previous XCode versions(xcode3). However this does not work for me.
Thank you

Answer 1

I have just tried downloading xcode3 from developer.apple.com using firefox, and the resume in firefox works fine, even after a firefox restart.
The app downloader had over 4gigs worth of data saved, then there must have been some problem, then the amount of data saved must have gone back to 0.
How does the app downloading program decide to zero out the saved file data? Is there any way to inflence this or somehow make manual backups, like I could with firefox.
I do have broadband, but its a slow broadband. I did have to reenter my username and password a few times during the download process, probably because there was some sort of cookie expiry happening. However this worked fine.  However something went wrong at the end. maybe it was because I clicked the retry in the pop up, rather than the retry next to the app store download progress bar.
If there was a flag or something that said whether or not to resume or retry from scratch then I could maybe edit that and it would help.
What happens now is that when I click pause, the data is written to the .pkg file, which is correct.
However when I click resume the file size immediately goes back to zero.