Hello! My name is XXXXX XXXXX self-employed tech, and I'm offering my time in good faith today to assist you on this question.
OS X 10.5 was released on CD/DVD only and is not available as an online purchase. This release is no longer offered at retail, however, but can be regularly found on eBay and Craigslist as people/merchants get rid of old stock. Buy-It-Now pricing on ebay seems to hover just over $100.00 for a full version.
Once you have obtained a physical copy, it can be installed as an upgrade over your existing 10.4 installation. However, I would personally recommend doing a clean install (erasing the hard drive before installing 10.5). Whichever way you choose to go, I would recommend backing up all important info before proceeding.
If your system supports it, I highly recommend upgrading to 10.6 instead. It is more widely supported now and can be purchased for only $29 directly from the Apple Store.
If you need more information concerning the above (or have additional questions) just replay straight back to this thread and let me know:http://www.justanswer.com/mac-computers/5ro7r-mac-os-v10-4-11-computer-need-update.html
Hopefully, this info will answer your question. If it does, please click ACCEPT so I can be credited for assisting you today. If you continue to have questions on this topic, DO NOT leave negative feedback, just reply back to this thread. I will be more than happy to work with you further.
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