Bigpaws' link is a good one.
edit: I reread your post and saw your main concern is burning up your download limit. Ignore the stricken text and proceed to the instructions for wget ("Code:").
Use the browser you posted here with. Be sure to right-click on the link and choose "save link as" or similar. If that works, you should grab this too:
Read the md5sum command below to verify your download.
Surest way I know of is open a terminal and:
wget -c http://ftp-osl.osuosl.org/pub/vectorlinux/VL64-7.0/iso-release/VL64-7.0.1-STD-FINAL.iso.md5sum.txt http://ftp-osl.osuosl.org/pub/vectorlinux/VL64-7.0/iso-release/VL64-7.0.1-STD-FINAL.iso
The "-c" is for "continue". It's ok to use this on the first attempt; using it on subsequent attempts should allow you to complete an aborted download rather than starting from scratch. The first URL there grabs the md5sum so you can verify your download.
md5sum -c VL64-7.0.1-STD-FINAL.iso.md5sum.txt
It should return "VL64-7.0.1-STD-FINAL.iso OK".
The md5sum.txt file is very, very small, and restarting downloads with wget is cheap as far as data use goes. Of course you'll still use the amount necessary to grab the file, but you should have a good one when you're done. There's a way to try starting with any partial file you have, but I give it a low chance of success and don't suggest it.
edit: Changed my mind. mkdir download, cd download. If you have a partial file (mostly complete from what you said) copy it here. Be sure the name matches. If not, mv <oldname> VL64-7.0.1-STD-FINAL.iso Then do the complete wget and md5sum commands from above.
If the filesize you have is what you say, trying this first will cost very few bytes. If it doesn't work, delete the ISO, take a deep breath, say bye to most of another GB of use, and rerun the wget and md5sum commands. OR: there's a way to lop off the last several bytes of a previous attempt and try again using "dd". If you'd like to try that, post back. I probably won't be here, but someone else will know what I'm saying and send the info.
Good luck, HTH