I What to put my OS on an external USB hard drive (and boot from the external HD) then use the internal hard drive for storage only. I tried doing a new install of the OS on the on the external HD the install started OK, when the install found the existing OS it asked if I wanted to install to C: (existing) or G: the external USB HD (I have 2 internal hard drives, 1 DVD reader and 1 DVD burner thus the drive letter G:) I choose G: and got a messsage that G: was not assesable for this without additioal software. Is what I am trying possible and if so how?

Is what I am trying possible and if so how? most likely since windows xp recognizes usb drives when searching for discs during the installation. your bios must support 'boot fro usb' does it make sense? certainly not, if you value perfomance. usb: Hi-speed devices are advertised as "up to 480 Mb/s", but don't actually operate at that full theoretical (60 MBytes/s) data throughput rate. The maximum rate currently attained with real devices is about half, 30 MB/s. Most hi-speed USB devices typically operate at much slower speeds, often about 3MB/s overall, sometimes up to 10-20 MB/s. SATA 1.5 Gbit/s: actual data transfer rate of 1.2 Gbit/s, or 150 megabytes per second (MB/s) SATA 3.0 Gbit/s: actual data transfer rate of 2.4 Gbit/s, or 300 MB/s ... even normal ide drives operate much faster than usb devices. Today's subliminal thought is: 'Calm down ... it's only ones and zeros.'

Apperently its not as easy as it could seems...me too was trying install xp (or any other OS for that metter) on a USB flash drive - was unsuccessfull...gave up on it...

It is possible to do but you have to reconfigure some key registry settings in order to do it...but as mattie pointed it out...extremely slow regardless of what type or amount of ram you have. If I remember right there are about 25 different registry keys that have to be altered in order to use an USB or flash drive as a bootable media for XP. In The Matters Of Style, swim with the current; in matters of principle, Stand Like A Rock "People demand freedom of speech to make up for the freedom of thought which they avoid."

It works perfect, but you need to modify some files

Dude, Certain things are better handled in specific ways. It is possible to fall asleep while standing upright and perhaps even eat & drink beer standing on our heads. Now, for all intent & purposes, is it practically convinient? I don't know - but if you answered yes, you are a definitely one of them good freaks! Don't make things overly complicated for yourself, if you don't have to or not trying to make a point. Good luck!