Thank you for answering. Someone told me I may lose files if I install windows 7.
If you do a clean install of Windows 7 (format C:, then install), then yes you will lose all the data and programs you have installed on the C: drive. If you are doing an in-place upgrade (like going to Win7 32-bit from Windows Vista 32 bit, or 64-bit to 64-bit) then your shouldn't lose any data. If you are going to W7 from WinXP then you have to do a clean install, regardless. Any clean install will erase any programs or data left on the install drive. Data on other drives will not be affected.