Vista - -> Copy so slow the machine almost freezes. Why? <-

Hi,
I have copied a 9.8Gb data file from my former laptop under XP Pro SP3
onto an external USB2 hard disk. This took 8 minutes.

Now I want to copy back this file from that same USB2 Hard disk to my
new laptop. A fresh out of the box Vista Business 32bit copy to which
I have applied all fixes, it's under SP1 and I have also fine tuned it
following instructions from the forums and the web where people were
complaining about the copy speed problems (officially fixed by Vista
SP1):

Search Indexing is disabled.
Disk sharing is disabled.
No Firewall, no Antivirus
ShadowCopy disabled
Killed that stupid TrustedInstaller process
Remote Differential Compression disabled
Removable Storage Managment enabled (supposed to improve USB devices)



System Idle stays aroud 88% (meaning it doesn't do anything) and still
the system is almost non repsonsive while copying that file.

The 9.8Gb file copy back fro mthe USB2 disk to my hard disk took 1hour
27 minutes. Averaging at about 2.3Mb/sec

Is this serious?
My laptop currently has about the fastest processor available, and all
USB ports are of course USB2. The Hard Disk itself is USB2 as well.
4Gb of RAM and plenty of room on my local hard disk.

And copying to a hard disk is usually 3-4 times slower than reading
from it, isn't it? So how come we WRITE in 8 minutes and READ
(supposedly faster) in 90 minutes?

Also I tried a dos xcopy command to avoid Win Explorer, and also used
TotalCommander to copy back my file.

Any suggestion?

My Vista edition is called "Business". But there is no way to run my
business using such amazing performances. I'm a data cruncher and get
quite often Gb of files. I can't spend every day half a day just
getting those files back to my hard disk. Or should I invoice
MicrobeSoft for that time?

Besides reformatting and UPgrading to XP Pro again, any other way to
fix this? Looks like computing like it was done in 1988.

Thanks for any help.