Those who are still using Ubuntu 7.04 (Feisty Fawn) are advised to upgrade their distribution to later releases as it approaches end-of-life support, this October.
What is end-of-life ?
End of life means that the time where a product is no longer supported by its vendor. In case of Ubuntu 7.04 (Feisty Fawn), it will no longer receive security updates and patches. Normally this would not cause problem to desktop computer, but if you are advised to patch your system as regularly as you can if you are connected to the internet to prevent malicious user from accessing your pc.
Curious about how long other Ubuntu releases are being supported? you can refer here : Ubuntu Releases and end of life date