There's no need to go right back into your archives to install the very first full version of the software in order to install the latest upgrade that you own.
Even on a new computer with no Adobe software previously installed, you only need to load the very latest upgrade, enter your upgrade serial number and the installer will ask for a serial number from an earlier, qualifying version. You can then enter a previous serial number (even it that was an upgrade) and the installer will continue.
That said, Adobe decommissioned the CS2 activation server last year so your version will no longer work anyway.
See here for non-activation versions of CS2 which Adobe made available to existing CS2 customers - complete with brand new serial numbers. This is the CS2 version you'll now need to install.
http://www.adobe.com/downloads/cs2_downloads/index.html
http://helpx.adobe.com/x-productkb/policy-pricing/creative-suite-2-act ivation-end-life.html