The default 512MB of your VM is plenty, especially if you're configuring swap during install. I'd revert to it to save memory for running Windows programs.
Please check the md5sum. Use one of the utilities from the linuxquestions link above, or fciv. You should get
f3cf3a7a352bb36757c2e21499762d73 (This really should
be conspicuously posted next to any download link, but often isn't)
The directory http://ftp-osl.osuosl.org/pub/vectorlinux/veclinux-7.0/iso-release/
contains the ISO (.iso) and its md5sum (.iso.md5.txt).
It's good to have a file checksum utility, as it would apply to nearly any distro you download; they "all" have an md5sum, or maybe an SHA256/512 sum. If it doesn't match, download the ISO again.
It probably matches. In that case, be sure that the virtual HD you're installing to has at least 8G, and that the part mounted as "/" (root) is allotted at least 4G of that. If other distros are installing, you probably already have this, too.
That leaves a problem with the ISO or installer itself. You'll get plenty of help here with that, but it can be more than you bargained for. Depends on how interested you are in VL in particular, running on a VM.
That's where I should leave you, as I'm running a different (Light) version of VL, and don't usuallly use VM's. Many do, though, and you'll get replies if you want to go on and post how much disk space you're allotting and whether the md5sum is correct.
In any case, thank you very much for the feedback so far.