after i install windows7 on my laptop, will i have to reinstall all of my programs? and will i lose any data from my programs?
If you are using Windows XP or Windows Vista, you will not lose any data of your computer. Because after you inserted the installer CD, your older Windows will upgrade it.
Exactly, some big programs will be not working (e.g. Adobe Photoshop) because the registry of the Windows will be resetted, and some small programs which not needing registry will be working as well (e.g. Mozilla Firefox).
Before installing, i recommend you to move all important data to another drive partition, example save important data to "D". Because the installing process will harm your data which saved in "C" (that's why the registry resetted).