Hello All! I'm new to the forum, I wanted to register because I think this forum is very effective and there's a problem driving me MAD lately.
I'll try to be as specific as I can.

I'm pissed off since I got my router to connect 4 computers with internet in my home because it keeps droping my conenction, timing out my big downloads and so on.

Here's how it goes:
The internet comes in fiberoptics to an Arris TM501A Modem directly from my ISP. This moden also uses VoIP and I got it connected to my phone, the phone always works fine as well as the modem. So before buying 4 new computers one laptop included, I got it connected directly to my computer and life was good. I bought this Belkin Wireless G Router F5D7230-4 the typical one with 4 ethernet ports and the wireless option.
I got my network working and all good even the wireless, theres 3 wired computers and 1 wireless and I can access all the network and all the computers have internet can surf, download etc.
The problem comes when I start to download 10MB or larger files the connection starts very good until it reaches 15 to 25% it drops and looses connection to the server.

Lately I deactivated all my security and firewalls and the downloads actually finish but in a huge time because the server still looses connection to my computer for 1 or 2 minutes then it resumes (with a download manager software) the log just shows: server does not respond then it tries again and so on so on.

Here's a little graphic to show the drops:

Anybody can help me out? Please! If anyone need more information to help me out just ask!
Thanks!!

I don't know exact answer but I can give you plausible causes from my experience. You have to do trial-n-error solutions.

My experience:
1) Once I tried to use Cisco (old) DSL modem to hook up to my Verizon DSL connection. Initially, everything is fine. A day later, it crawls to like less-than-modem speeds. I tried fixing many things including changing MTU sizes (below) but no luck. Finally, I assume that equipment is incompatible and gave up. In your case, you can research on whether Belkin model is compatible with your connection and if not, give it up.

2) You can adjust your MTU size on your Belkin to a lower number like 1300 (no less than that). But I don't think this is the cause coz you have much faster upload bandwidth.

3) Your ISP can be controlling your bandwidth on their side. But I don't think this is a problem either since they allow you to have VoIP and that's bandwidth intensive.

So the cause I think is most likely to be the incompatibility.