Wireless Internet forum: New Router, Slow Speeds

A little while ago my internet got really slow. So I did some tests and found out that by connecting my laptop, or any other computer to the modem fixed the problem. So I bought a brand new router, got it set up and the same problem remains. This is found in both wireless and wired. The speed seems to be erratic. Some times it will be will go up to 3.5mbs (at best), and other times it will be as low as 0.5mbs.The isp is providing 5mbs which can be easily obtained by by-passing the router. The speed seems to be fine after a restart of the router, but after a few minutes it goes down to like 0.5-1 mbs. This is unnacceptable being that I just bought this new router. Its a TP-Link WR1043ND. I got it off of Newegg. Most of the reviews were quite good. My old one was also a TP-Link. It was obviously a much older model, WR42G. It served me well for about 4 years. The new one is supposed to have speeds up to 300 mbs. The mode that it is on right now is only 130mbs. However that should not matter. The Modem is only putting out 5mbs, I should have plenty of bandwidth to use. There are only 4 devices connected at the moment. 2 computers, (neither running any p2p, online games etc), an I-pod and a printer. It is password protected so there is nobody stealing any bandwidth. It does not drop the signal at all and the speed seems to be the only problem. I've also tried different ethernet cables between the modem and router. As was mentioned the speeds are erradic. It can be half decent, say 3mbs and after pushing test again, will go down to 1. I don't know why this is happening and would appreciate any help anybody could give.

*All speeds are for download, and all were obtained via speedtest.net using the same location to test.

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