Windows 2000 needs 64MB of working memory. A reasonable amount of memory for running applications as well is 256MB, which is why I chose that amount.
Windows XP can work with as little as 64MB of working memory, but in practice it recommends, and thus requires, 128MB of working memory.
I've tried Windows XP using a friend's system with 256MB of RAM. It slows down to a crawl when you do something as simple as open up an explorer window while running an application. So it needs at least 512MB to work properly with applications.
The memory alone might be cheap to get but I'm interested in the system as a whole in terms of all the system components balancing each other out.
This is the specification for the Windows 2000 system previously mentioned:
AMD Athlon XP 2200+ processor
nForce2 motherboard
256MB 266MHz DDR SDRAM (using 2 x 128MB DIMMs)
DVD-ROM and CD-RW drives
40GB Ultra-DMA 7200rpm hard drive
1.44MB 3.5" floppy drive
64MB ATI Radeon 9200 AGP 8X graphics card
17" FST 1152 x 864 @ 75Hz colour monitor
etc.
And this is the upgraded specification I personally feel would be required to work with Windows XP:
AMD Athlon XP 2200+ processor
nForce2 motherboard
512MB 266MHz DDR SDRAM (using 2x256MB DIMMs)
DVD-ROM and CD-RW drives
80GB Ultra-DMA 7200rpm hard drive
1.44MB 3.5" floppy drive
128MB ATI Radeon 9200 AGP 8X graphics card
19" FST 1600 x 1200 @ 75Hz colour monitor
etc.
So you see why I would feel that I would have to go for a significantly more expensive system to be comfortable with Windows XP? This would in turn mean waiting several more months before I can finally have a system to run my copy of DarkBASIC.
Yoda I talk like when drunk, yeess!