[manjana]

How do you know these are free of any malware?

[bsagdiyev]

For Windows ones the SHA sums are available online to compare to.

[boomboomsubban]

You can make SHA sums of malware.

[schroeding]

If the ISOs are untouched (so it won't work for the posted "Delta Edition"), you can search the SHA hash of the version from MSDN. Relevant search keywords are "Microsoft SHA1 Hash Archive" :D