proteus 6 demo simulation fatal error...pls help!!

proteus cannot open sdf

i must say that..that problem doesn t exist with another computer.
i tried it my friends computers and there wasn t a problem..
and cause of that i formated my comp. but it didn t help to solve it..
i tried to run a file in samples directory..( i tired all samples..)
thats the log..::

SIMULATION LOG
==============
Design: Atmel AVR Tiny15 Demo
Doc. no.: <NONE>
Revision: <NONE>
Author: <NONE>
Created: 07/03/02
Modified: 17/07/02

Compiling source files...
Processing t15demo.asm...
up to date.
Build completed OK.
Compiling netlist...
Linking netlist...
Partition analysis...

Simulating partition 1
PROSPICE Release 6.7 SP0 (C) Labcenter Electronics 1993-2005.
SPICE Kernel Version 3f5. (C) Berkeley University ERL.

Reading netlist...
FATAL: Cannot open 'C:\DOCUME~1\ERHAN˜~1\LOCALS~1\Temp\LISA7928.SDF'.

Simulation FAILED due to fatal simulator errors.

------------------
it says cannot open lisaxxxx.sdf file
this xxxx always change when i run a sample..
note: sorry for my english it isn t good enough...
thanks for ur helps..

proteus 6 demo

could be a os related error.
are you haveing the same os on both the machines?
please check.
hock

proteus fatal error

sorry.. i m a beginner.. i don t understand what "os" mean..but i can say that there aren t any errors at the other machines..
thanks for ur interest..

Added after 5 minutes:

himm if os mean operating system.. i use winxp prof. the others are same..
if necessary i m writing my machine properties..
128mb ram.. celeron 1.1ghz...(but i can say i tried that in another computer which is same with my comp.. and also same os)

Added after 2 minutes:

and i also wanna ask that.. it might be a hardware problem??