Upgraded LINUX not Working after upgrade

Hi,
Due to virus attack I recently upgraded to LINUX and the installation was successful as at the time of installation. As at the time of installing I didn’t get any error and now at the time of booting it just keeps showing as Loading, please wait.
The version of Ubuntu is 8.04.4 LTS, kernel of type 2.6.24-28 of type generic. Please help me in solving this.
Thank You.
