Windows simply has not kept up with hardware improvements and by the time 7 is released it will have fallen even further behind. The past 10 years have seen memory increased by a factor of 30, CPU speed and design improve from a single core 450MHz Pentium II Processor to a quad core 3GHz design. Hard drives have jumped from 16GigaBytes to 1.0TeraByte, not to mention the access and data transfer improvements. Simple 16MB AGP Video cards common with Windows 98 now are now 3D graphics power houses that include dual graphics processors with a gigabyte of memory and a PCI Express interface.
Where is Windows, well we still have DLL files, a registry that everybody either loves, hates or wants to clean (there are more registry cleaner utilities available then brands of detergent to clean your clothes), a pagefile and either FAT or NTFS formatted hard drives all of which have been around more than 10 years.
What Windows 7 should be is an OS that takes full advantage of today's hardware and the 8, 16 32 and on up to 256 core processors along with the other changes just around the corner.
A user should be able to specify how each of the cores are used. For instance on an 8 core system, 2 cores (or more) could be assigned just for the operating system, another two cores for applications, 1 core for graphics, 1 core for other I/O tasks, 1 core for background applications like AV software and the one remaining core held in reserve and automatically allocated to any task that may be loading down one of the other seven cores.
You should also be able to assign priorities to applications so that for instance the streaming video software gets more CPU time than your picture editing software if both are running at the same time and email is running at a lower priority then your word processor.
Don't want all the configuration complications, Windows should provide several default configurations for processor core allocation and software priorities that a user can choose from.
I know it's not likely that any of this will make it into Windows 7, but whatever 7 should turn out to be, it better be a lucky number 7 or there just may not be an 8.