I don't think anyone is responding because at the price you mentioned, it is going to be almost impossible with the requirements you mentioned.
A desktop yes (without a flat panel), notebook (IMHO) no.
If someone could meet those specs at that target price they would put everyone else out of business.
As to 802.11n, I am not that excited about it. Sure, the promise is 600Mbit/sec but why spend the bucks when it all goes to an access point probably running 6-10Mbit/second on some cable modem. (DSL even slower [in homes])
I have used all of the Microsoft operating systems, Mac OS and some Linux variants.
I guess it is fun to kick Vista and pontificate to those less knowledgeable that "Vista sucks", but I don't see it.
I run Vista on a desktop and a notebook (Other notebook are running XP.)
The notebook does fine on a Centrino Duo chip with 3Gb of memory.
I think a lot of complaints come from people who tried to upgrade old systems. These systems had a lot of crap in their registry, viruses, trojans, cookies. On top of that they tried to get it on systems that probably wasn't up to the task because Microsoft was too optimistic. (Be real, there is no way you should run Aero Glass on a Pentium 4 with 512k-1Gb of memory. )
I also think that long time users of XP are frustrated with Vista because it looks different and all of the familiar things are in different places. I am not sure what you are running now but if you are moving from something less than XP then you are going to see a change anyway. It may not affect you that much.
But, if you have to have XP I think HP has a "downgrade to XP" option on some of its business notebooks. But, you are going to get them for the price you mentioned and do everything you want.
There is one of these HP machines that get close, the 6730 business machine. http://h10010.www1.hp.com/wwpc/us/en...5-3687778.html
You are going to have to choose "Configurable" and deselect a lot of options to get it to that $549 price.
I am sure Dell and Lenovo have similar models.
I don't think anyone makes a consumer grade notebook with XP anymore.
You can get some cheaper consumer notebooks but they aren't as sturdy, or last as long a business class notebook in my opinion. Most consumer machines that are moved last the average life of a PC (2-3 years).
But if they don't move it why did they get a notebook?