After formatting and reinstalling Windows which softwares did you installed in your system? If possible then give the order of softwares that you have yet installed.
By the way, I am assuming you have installed Vista from screen-shots. Is it Vista or XP?
Did you put (before installing Anti-Virus) any CD/DVD disc or attached USB flash disk?
This error actually comes up if the check sum on EXE (setup file) doesn't match to what is written in file. PackageForTheWeb component is used by setups made by InstallShield. It might be possible that some setup was left incomplete and that is making problem. You can visit their website and look at following KB and try to do the written steps:
By the way, you should run Memtest86+ from following web-site (download it, burn it on disc/flash, boot from disc/flash). Let it run for at least an hour or more until it check RAM at least 3 times.
Also check that your processor is not getting to hot. Processor can also make strange errors if it get too hot.
There should be enough free disk space in boot drive, especially in partition in which your pagefile is present and in paritition in which your temporary folder is present. If you haven't changed anything it is usually C:. Make sure there is at least 1GB is free in C:
If RAM is cleared and okay and processor temperature is not too hot (check it from BIOS after RAM test is over) then try to download AVG (or any other FREE antivirus, not cracked, from their website) and try to install it. If it get installed then scan all of your HDDs (not just C:, all partitions and all files).
If it does not get installed (most probably) and if you still don't want to format then try as following:
1) You'll need another computer to complete this job.
2) Remove your HDDs from your computer (all of HDDs).
3) Attach your HDDs as slave or secondary (one by one) to another computer.
4) Boot that computer using its own master drive (while your HDD as slave).
5) Windows will detect your HDD (that you have just attached).
6) Install any good anti-virus with latest definitions then do a full scan (all files) of your attached HDD.
7) After it shows that it is clean. Repeat cycle for all of your HDDs.
If all fails, then you'll have to format your HDD and reinstall Windows but remember that you should install Windows from a reliable CD\DVD disc (to make sure that it doesn't have virus in it) and you should install a good anti-virus just after installing Windows (before installing anything else, even not drivers). While you are installing Windows, Anti-Virus and drivers, do not attached your computer to internet. Unplug internet cable/wires etc. After you have installed everything and raised your firewall then connect to internet for upgrades etc.
Do tell me how's it going? Update us with your progress.