Copying lots of smal files starts and stops - VERY slow.

I'll describe my system below, but here's the problem.

When I copy lots of files (even small ones) from anywhere to anywhere using
a variety of methods (eg backup software; folder drag 'n drop; the copying of
all the small scenery files when installing Microsoft Flight Sim), I get the
same problem - fast and continuous to begin with, then it stops, copies a
dozen or so files, stops, copies a dozen or so foles, stops, and so on.

There is one exception so far. After recently trying a variety of backup
softwares, I found that BackUp4All can copy 125Gb of files without slowing
down or getting into 'start-stop' mode.

My system is WinXP Pro on a 2.4GHz CPU with 1.Gb RAM, 80Gb HD on the
motherboard for software, 2 x 200Gb HDs on a RAID 0 controller (my problems
started before the RAID controller was installed) for Documents and 500Gb
external USB 2.0 disk for backup.

Any help and advice would be appreciated.

Steven Lyall