Computer geeks, this is your time to shine.

[Josquius]

Defragging couldn't do any harm. May not solve it but worth a try, could be fragmented to hell?

My 2*1TB HDs are divided in 8*250 GB partitions (1 system, 1 docs, 2 games, 4 vids & assorted)

I don't see why a defrag would do anything... 

KEvin

I'm guessing if its totally fragmented then the download could get corrupted due to being placed very oddly in the file structure. Just a random theory in lieu of a definate answer though.

[Iormlund]

Another vote for bad RAM. Try memtest86.

[DontSayBanana]

RAM's one answer. How full are your partitions? I realize 2TB is pretty hard to fill, but I also know people who do their damnedest to keep that amount stuffed- NTFS isn't as bad as FAT32 about disk thrashing, but it still has a comfort zone of somewhere around 128MB, in my experience.

[dps]

I'm far from an expert, but I'd say it's possible that your flash player or other media player either aren't the latest versions or have corrupted installs.

[DontSayBanana]

The old versions shouldn't have anything to do with the installers for the new versions. Also, are you using a download manager, like GetItNow or FlashGet? I think both updaters you're talking about come in the form of self-extracting archives, and download managers make a lot of archives' CRC checks fail.