I have installed Microsoft Security Essentials [MSE], a free download from the Big M.
I removed Avast and Windows Defender.
MSE will be the anti-malware software of choice for Windows 7 [W7]. It will not be included in W7 because that would invite more law suits from people like Symantic. And, of course, the user will be free to adopt any existing anti-malware software.
I will be buying a new machine when W7 is launched. It is really for my wife's use, replacing a PIII; but I get the "underneath". The I7 CPU from Intel is four core and hyper-threaded, so I will be able to crunch on eight work units [WU's] for BOINC and WCG at the same time. My two Core 2 Duo processors are not hyper-threaded so they each crunch on two WU's at one time. The 1.6 gig Atom N270 in the netbook is hyper-threaded, so it does two WU's at once, each twice as fast as a one gig PIII in the machine that will be replaced, b ut at 1/11 the speed of each core in the Core-2-Duo machines.