is it time for MS to start from scratch with its OS?

Apple can do this because they don't need to support as much Hardware as Microsoft does.
With Apple you pay for it as in expensive Hardware and Apple telling you what you can and cannot Upgrade to.
With Microsoft you get a wide selection of Hardware choices. You can go really cheap or really expensive. It's really up to you. In the past you also paid for this with the occasional bad driver support. With Vista that changed as Drivers had to go through a testing process and believe it or not people bitched about that too as some of their crappy hardware wouldn't work anymore.
I haven't had Vista crash on me since installing it unless I'm OC'ing in which case it isn't Vista but me. I use Hibernate which upon turning on my computer puts me back up and running from where I left off in 30 seconds. I tried all the OS's.. Linux, Mac Leopard, even XP and it was all fail. Vista is a pretty remarkable OS compared to them all. I'll begin with XP.
XP... Wireless Networking. After a day of trying to get my Wireless Network to work on my son's XP machine I installed Vista. One to two mouse clicks later and I can tell you I will never... ever... install XP on anything ever again.
Linux... All that stuff about Linux being easy was a lie. It isn't a very friendly OS at all. I really wanted that free OS but to be honest it wasn't very free but more like a big pain in the ass. I like using my Computer to do all different type of things including playing Games like CoD4 and Bioshock.
Apple... I did this Leopard Hack to just see if the Apple OS was worth it. It wasn't.
I don't really understand how I used XP. Before I went to Vista I used it without much incident. Now it feels clunky and nasty. It took two days to get XP loaded fully on my sons computer. With Vista it took around two hours.
So I don't want it to change. It's faster than my old XP system, never crashes (unless I'm screwing around forcing it to crash), runs on a ton of hardware, runs a host of entertainment junk, and was incrediably easy to setup.
I couldn't ask for much more.

gta, if the rumors that were floating around are true that Windows 7 will be 64 bit only, then alot of the legacy support will no longer be carried forward. This is because 64bit OS cannot run 16bit code (99% sure on this but could there be a loophole?)

With that said though... if I'm using older equipment at work then I'm not looking to upgrade unless it breaks or something significantly better comes along. For instance, some of my equipment that I used to work on runs with 386 processors in it because anything faster would be a massive waste.