I need to urgently do something about it.

The steps, which a ppt recovery online for this solution, are shown below:

1. Open  program. Click on Office button (on top of the left side).
2. A window will be appearing. Now select corrupt PowerPoint file from the system directory.
3. Click on the arrow of Open button. A list will be scrolled down.
4. From the list, click on Open and Repair. After some seconds, the file will be repaired and opened.

which recover ppt online for this solution, are shown below:
1. Open MS PowerPoint program. Click on Office button (on top of the left side).
2. A window will be appearing. Now select corrupt PowerPoint file from the system directory.
3. Click on the arrow of Open button. A list will be scrolled down.
4. From the list, click on Open and Repair. After some seconds, the file will be repaired and opened.
Note: Though this solution efficiently works with corrupt files, but if it does not work we must try the following solutions.
1. We should try to open a corrupt file in OpenOffice.org Impress.
2. We should try to open a corrupt file in MS Word. If it gets opened, we can recover at least the text part of the presentation file.
3. We should try to import the slides from the damaged file into a new file.

The link in the above post is not an official Microsoft source.  Be careful with it - using it could result in the compromise of personal information.