Yes but for me to tell you how I need more information if u would like to know how message your computer specs
Windows XP doesn't directly determine what type of memory can be used; it depends on the motherboard. If the motherboard is compatible with Windows XP and the motherboard supports this memory module, then you can use it with Windows XP.
XP - 256mb (1gb recommanded) 98 - 512mb (recommanded)
No. Windows XP has it's own kernel and memory management system.
About 1Gb, I believe.
I would suggest at least 1Gb of Ram and at least a 32Gb Hard Drive
Yes, but much slower than it would run Windows XP or a Linux distribution. Make sure your computer has at least 1GB of RAM to run Vista decently.
You cannot run Mac on Windows XP. But you can run Windows on Mac
You can compress your files into a spare harddrive to keep your memory ok
Tally 6.3 run on windows XP
Yes ofcourse, Windows Vista is upgraded version of Windows XP. Obviously it can run Windows XP applications.
You don't 'set' the memory size, you need to add physical memory.
They are "compatible" in the sense that many applications that run on Windows XP will run on Windows Vista.