Run ScanDisk or a defrag program-- quite often when there is a non-fatal disk error, Windows will misreport the amount of free space on the drive in My Computer.
It would seem that you don't really
have 1.4 GB of space, otherwise the file should be copied to the HDD properly.
Are you downloading these one at a time? You don't have enough space to download 2 ISOs at once (what with temp files and all), so if I was you, I'd try downloading one ISO, burning it (in case you don't know, you must use the 'burn image' command in a CD burning program like Nero or EZCD Creator, do not
burn the *.iso file as a data file--many people make that mistake), then deleting the *.iso file and downloading another one.
Also download the *.md5 sum of the ISO and use an MD5 checker such as Brad Smtih's Easy MD5 Creator
to check the download before burining it-- it would be really painful if you wasted time and media on a corrupt download.
Hope this helps.