New Maxtor 300GB external HD shows ok on device manager but WITHOUT drive LETTER and can't be accesed - running WinMEHas that drive been partitioned and formatted yet ? ?
If not Windows will not see it.
Use the MaxBlast utility that shipped with the drive to PREPARE it.

patio. Hmm...
did u make sure to format it properly?
insert the WinME cd into the cd-rom, reset ur pc
when the 1st screen shows up (memory count, the display of your harddrives), click on "del" buton a few times till the Bios windows shows up, go in:
Advanced Chipest, or something LIKE that, i dont remember excatly...

anyway, change the Boot order, instead of Floppy, choose CD-ROM, Save&Exit.
when ur pc restarts it self, it'll ask u to press any key to boot from CD-ROM, FOLLOW this instruction, be patient 'till the screen shows up showing all of your partitions, try to format/re-format your harddrive (NTFS/FAT32), and create a logical partition.

If that didnt work, start your pc, in windows, right click on My Computer >> Manage >> Disk Management >> try to see what details does it show you bout ur Maxtor hard-drive & partitions.