Lost DW [CS3] in Computer Crash

The aging CS3 activation servers were taken offline a few years back.  Even if you had the old installation disks, you would not be able to activate the software. 

Assuming you have a compatible operating system -- Windows is more backwards compatible than Mac -- and a legitimate CS3 serial number which you can get by logging in to your Adobe Account, you could obtain a replacement CS3 installer and serial number that does not require online activation.   See link below for details. 

https://helpx.adobe.com/creative-suite/kb/activation-fails-cs3-acrobat-8.html

As Test_Screen_Name mentioned, there is no upgrade path for any Creative Suite product anymore. Everything is now done via subscription under Creative Cloud, but don't let the name fool you. The programs are still installed on your local machine, they just need internet connection from time to time in order to verify you have a valid subscription.

Plans are available here: https://www.adobe.com/creativecloud/plans.html

You could have upgraded when CS4 was released in 2008, or when CS5 was released in 2010. Once CS6 was released in 2011, the time for reduced price upgrades for CS3 customers was passed. Anyway, Creative Suite was replaced by Creative Cloud in 2013, and no updates would even be possible; it is now a subscription-only product. All apps from $50 per month, single app from $20 per month, Photoshop (special) from $10 per month. 

IMPORTANT: someone may reply telling you to email. They may then offer to help you get Creative Suite. This is a SCAM, and you would get no legitimate product for your money (plus, scammers would have your credit card number, never good).