What version of Windows / service pack will you be using?
You didn't mention the exact model of your Toshiba Tecra S3.
But it looks as if most of the Toshiba Tecra S3 models had SATA hard drives so I'm thinking the 500GB model you bought should work.
Should be no problem installing the HDD in the laptop, Just verify sata vs Pata (I did not look your laaptop up), all recent laptops use the 2 1/2 In SATA HDD/SSD,.