I'm looking to get a wireless adapter for a desktop. The desktop is on the first floor of the house, and the router is on the second floor. The router is a Netgear WNDR4500. Windows 7 OS.

I'm looking for the best wireless adapter in terms of maintaining a connection, throughput, and speed. Suggestions?

these will do it for sure.

http://www.radiolabs.com/products/wireless/waverv2.php
or
http://www.radiolabs.com/products/wirel ... -power.php

have you checked to see what wifi channels are less crowded in your location? omni directional wifi routers send their signal in a horizontal doughnut. sometimes a small directional antenna conected to any wifi card, so you can aim it at the router, will work well when going between floors.

have you checked into powerline Ethernet adapters yet?

Since you have a 3 stream dual band router you want a 3 stream dual band card for best throughout. Like with wired NICs, Intel is one of the best in wireless as well. The Intel Ultimate-N 6300 is their current best which is dual band and supports 3 streams. I haven't seen any desktop Intel wireless cards, so you'll need to look at using a mini-PCIe card in a desktop adapter.

Something like this (no recommendation on the store, just an example):
http://www.bplustech.com/adapter/MP2W_6300H.html

If there is little interference in the 2.4 GHz band then use that. In the more likely case that the 2.4 GHz band is crowded then use 5 GHz. It has less range and penetrating power, but can work better if the band is clear of other devices.

If you really care about performance and you have a desktop you should really look at just biting the bullet and running a wire. Even in the absolute best case you will never get even close to the rated speed out of wireless. With a setup similar to yours and an Intel 6300 card I get about 240 mbit/sec real world about 3 feet from the router. Add a floor in between and the speeds drop significantly. Same laptop using the crappy wired realtek gig nic gets about 975 mbit/sec.

The matching same brand USB adapter - the Netgear WNDA4100 http://www.netgear.com/wnda4100#one - is the best option. Not cheap at around $60, but will deliver higher throughput and a more stable connection than the generic alternatives. The supplied desktop dock/extension cable is useful if you want to keep the front USB ports free on the PC.

As both the router and USB adapter support it, it would make sense to use the 5Ghz band, this should be clear of the channel conflicts and interference than can dog the 2.4Ghz frequency. It may also help to use the latest driver from Netgear http://support.netgear.com/product/WNDA4100.

I disagree. It doesn't matter which brand your router has, it matters which chipset it uses. 5 or 7 years back you were right, but today since reaching 801.11n i've seldomly come across any issues with "not-matching" WLAN cards and routers.

I use several of those cheapo RT30XX (http://logilink.de/showproduct/WL0049.htm). They come in at around 10€ and they are paired against a fritzbox 7570. Using speedtest.net shows nearly no difference between this cheapo stick and my notebook sporting full fledged intel WiFi.

One of my relatives had a Netgear router/generic USB 11n adapter combination which constantly dropped the connection. Replacing their adapter with the Netgear item transformed the situation. I did go to the trouble of measuring the throughput with both the generic and the Netgear, and the Netgear figure was significantly higher. But the issue was the reliability of the connection and that was fixed by the somewhat more expensive Netgear device. In the context of this thread, the option for dual 2.4/5.0Ghz operation is clearly going to rule out many of the cheaper generic devices, including the one you reference.

Given the necessary hardware support I would strongly recommending going for 5Ghz wherever possible. A useful piece of free software to help make this choice is InSSIDer wifi scanner from http://www.metageek.net/products/inssider/ which supports both the 2.4 and 5Ghz bands.

Sry, i missed the 5.0 GHz part.

And i second the thought of going 5.0 GHz, in my neighborhood are literally dozens of 2.4 GHz WLans but only a few 5.0 GHz ones.

Thanks for all the helpful info.