This is not normal behavior. It is hard to say what your problem might be. Has it always behaved this way? What are your system specifications? What graphics card are you using? What graphic card driver?
Below is my system specifications:
Model: Dell Precision T1500 Tower Workstation Desktop
CPU Type : DualCore Intel Core i3 530, 2933 MHz (22 x 133)
Memory : 2GB
OS: Win 7
3D Accelerator : nVIDIA Quadro FX 580
I'm not sure that SW2008 is supposed to run on Windows 7 It is no longer listed on the SW System Requirements page.
Two GB of RAM is not much, even with an older version like 2008. the SW System Requirements page lists 2 GB as the minimum, but I seem to recall seeing somewhere that 6 GB was the recommended minimum for a 64 bit system. Is your Windows 32 bit or 64 bit?
They also no longer list SW2008 on the Graphics Card Drivers page. I tried SW2009 and they still didn't list any approved drivers for your card. (It doesn't list the T1500 system at all and Dell systems often use a different approved driver than for the card itself.) For SW2010, it shows two drivers for either Win7 32 bit or 64 bit: 220.127.116.1100 or 18.104.22.16887. You might try those to see if it helps.
Another possibility is that you have a bad installation of SolidWorks. You could try repairing it or reinstalling it. It is safest to shut down your anti-virus software when you do the install.
thanks for your advice, my windows 7 32bit
i've try to repair or reinstall..
will let you know if my problem solved.