Problem Installing Quartus II v11.0 Web Edition

You downloaded the file three times -- did you check to see if any or all of the MD5 hashes of the three downloaded files matched the MD5 published on the altera web site? If the local file has a matching MD5 to the altera published value, your downloaded file's integrity would not likely be the problem.

You might want to check that you are following the guidelines about the installation path for the tools. Some tools will prohibit you from using installation paths that are too long or which contain certain characters "$!~/ :" or whatever. I don't recall the specific guidelines for what is restricted by Altera or Windows, but sometimes if you are having inexplicable problems changing the install path to something short and simple like "C:\Altera" is worth a try.

Also you might consider temporarily disabling or auditing the interaction of windows UAC and any anti-virus / anti-malware packages with the installer. Often such programs can disrupt the action of a complex installer program causing failures. Obviously, as you pointed out, Win7/32 is a supported platform for the tools, so they OUGHT to work with UAC enabled in the normal fashion, but still look for any installation notes/tips that may suggest otherwise. As for anti-virus/anti-malware programs, since those are generally not part of the Windows OS, there probably aren't any "supported" configurations for those with respect to Altera, so you're on your own to assess if they may be causing installation / use problems and to work around any that you may encounter. Often if you get something installed successfully then maybe it will run from that point with things like UAC or anti-virus enabled again even if you might have had to disable them during install.

DEP data execution protection is sometimes a problematic OS setting which when enabled causes some applications to not work properly. It SHOULD not be that, however, as that ought to go along with Win7/32 being a supported platform, even with a raised level of DEP in effect, but then again, maybe not. . .

Yes, the 5-post link thing is an annoyance and seems to be an ill conceived setting, simply making it harder for new users to properly cite references relating to their questions / comments..