Does your computer comply with the system requirements to run iTunes?
Windows Hardware
A PC with a 1GHz Intel or AMD processor
Screen resolution of 1024x768 or greater
Playing videos purchased on the iTunes Store requires an Intel Pentium D or faster processor
Playing HD-quality videos purchased on the iTunes Store requires a 2.0GHz Intel Core 2 Duo or faster processor
512MB of RAM; 1GB is required to play HD-quality videos
A DirectX 9.0-compatible video card with 32MB of video RAM; 64MB recommended
A QuickTime-compatible audio card
A broadband Internet connection to use the iTunes Store
An iTunes-compatible CD or DVD recorder to create audio CDs, MP3 CDs, or back-up CDs or DVDs
Windows Software
Windows XP Service Pack 2 or later, or 32-bit editions of Windows Vista
64-bit editions of Windows Vista or later require the iTunes 8 64-bit installer
QuickTime 7.5.5 or later is required (included)
200MB of available disk space
Screen reader support requires Window-Eyes 7.0 or later; for information about accessibility in iTunes, visit www.apple.com/accessibility