There is a platform swap process but it only applies to the current version (CS6)
http://helpx.adobe.com/x-productkb/policy-pricing/order-product-platfo rm-language-swap.html
Photoshop 7.0 is far too old to upgrade to any current version. Adobe's current one-version-back upgrade policy means only CS5 is eligible to upgrade to CS6.
Your options:
- Buy CS6
- Buy Photoshop Elements 12
- Join the Cloud
- Join the Photoshop Photography Program for $9.99/month