Assuming you are running WIndows XP on the motherboard in question, you can download from Microsoft their Windows 7 Upgrade Advisor tool:
Most likely problems are the audio and LAN won't work.
Windows 7 will install on your mainboard, but in order to use onboard devices:
- you must install WindowsXP drivers for 845G integrated graphics, and even after this you will not have Aero effects.
- you must get audio driver from Windows Update or from Realtek site
- you must install Vista drivers for 82562ET network adapter
AGP video boards also will unlikely work stable in Windows 7.
Also, Windows 7 have not good support for NetBurst-gen CPUs, so be ready for up to minute 'lock-ups' when using certain OS features.