Slow download speed and RAR file corruption on downloads

HI
I hope I am posting in the right place.

Here is my situation in brief. Specs will follow. My PC X is downloading faster than PC Y on the same connection with the same setup software except Windows and hardware. Now some details.

Hardware.
Internet. ADSL. Router Linksys 54GL firmware flash to hyperWRT some version - working hard for a long time without dropping any connections, sometimes non stop for months and months.

PCs.
X
Win 7 Home 64 BIT
Dell Inspiron 570 (almost the same configuration as my signature).
Dell motherboard, SATA II
Inspiron 570 in CM HAF 912 Phenom II x4 965 BE OC to 4.0GHz CM Hyper 612 MSI GTX 660, 180 GB Intel 520 SSD, bunch of WD RED NAS HDDs, 8 GB Corsair DDR3 1333, network from motherboard

Y
Win 8.1 64 BIT
Corsair Graphite 760T (bunch of fan upgrades, intake and exhaust), Asus Maximus VII Hero (SATA III), i7-4790K overclocked to 4.4 GHz (no turbo) with Noctua NH-D14, 500GB SSD Samsung 850 PRO as system drive, HGST NAS 3TB as main downloading drive plus WD 3TB Green for storage only, 16 GB 2133 ADATA RAM, network from motherboard.

Firefox is the same version on both PCs - v 28, and PaleMoon 64 bit the latest version, also the same on both.
Both PCs have the same version of NOD32 and Malwarebytes.
X Inspiron has firewall off and Y Maximus firewall is on.

Now the situation. I have uploaded.net Premium account, getting some huge files from there with different speeds. Older X Inspiron downloading at my DSL maximum speed, and newer Y Maximus download speed is limited to about 340 KB/s per file. I tried download managers, they provide high speed, but all downloads are corrupted - according to forums, it related to NOD32, but it is another story. I am using build-in FireFox download manager on both PCs.

Just tested the same RAR files on both PCs. Maximus get it corrupted (unsuspected end of the archive in WInRAR) and Inspiron got it in perfect condition, and Inspiron got it faster. WHY?

I don't get it. Older Dell (purchased in 2011 at the end of line life) is faster and more reliable for internet downloads than brand new Maximus based PC??????!!!!

I am very puzzled, help needed.

Appreciate for any help in advance.

It happened to me already and normally it's caused by memory errors. When memory gets corrupted before writing download cache data to disk you have a bad file. Try to exchange sticks positions, clean contacts or even underclock your memory just to see if it persists.

vrosa said:

It happened to me already and normally it's caused by memory errors. When memory gets corrupted before writing download cache data to disk you have a bad file. Try to exchange sticks positions, clean contacts or even underclock your memory just to see if it persists.

Click to expand...

Thanks for directions, that will take time - my Noctua fan (I hope not body) is covering some of my RAM sticks
Is it for certain or maybe - I noticed that single file usually get complete and multiple files, like part1, part2, part3 etc got corrupted, small files under 1 GB are usually OK.

Edit. Should I run Memtest or similar to check my RAM - I am still on warranty by Digital Storm, if RAM fails, too bad for them.

Edit2. How about download speed, why it is limited to about 340-360 KB/sec per single file, my older PC has no limiter?