right, i'd like to clear some things up:
1) Mac OS X can read, but not write to NTFS. this means that you can can see, use and open all of your files, but the drives are Read-only (like a CD-ROM). eventually, reformatting into FAT32 would be required for crossplatform read & write, or to the Mac's HFS+ file system.
2) Mac OS X can read Word 97 compatible documents out of the box in TextEdit, and as mentioned before, NeoOffice, the Mac port of OpenOffice can read all the rest of Office's documents. Outlook, though, i think has some compatiblity issues, so i would try and save those files in as open a file format as you can before porting them over, i.e. nothing related to Outlook.
3) the Intel Core processors used in all new Macs pretty much wipe the floor with most competing processors, let alone something as compromised as a Celeron. be aware though that as a modern operating system, Mac OS X is RAM hungry. 1GB would be fine, but i think 2GB is most comfortable, especially with the Rosetta 'emulation' layer, which is used for running older Mac software.
Dual 1.8GHz G5 2GB, 1TB, Radeon 9600XT 128MB, 10.5
20" Apple Cinema Display + Dell 2005FPW 20" dual-head
iBook G3 700MHz 640MB, 40GB, Rage128 16MB, 10.4, dying battery