Welcome to Microsoft Windows Vista Community site. For a better understanding of the issue let me know
A) From when did you start facing this issue, were you able to work successfully before without this issue; if so have you made any hardware / software changes?
B) Have any updates been installed recently?
C) Does any error accompany the F2 message? Mention the exact error message you receive.
I would suggest you to try out these suggestions and check if they can resolve your issue.
You likely have a defective CMOS battery or have lost the necessary boot files
Solution 1: The problem usually occurs because the CMOS battery on the motherboard is dead and the BIOS can no longer remember any settings once the system is powered off. Pressing F2 likely loads the defaults and allows you to continue.
Replacing the battery will resolve this.
Likely you need replace the CMOS battery. If it's dead, or nearly so, it won't hold the settings. Then when you boot up the bios detects that the settings have defaulted and asks if you want to go into CMOS / BIOS setup and correct things. Otherwise, hitting
F2 continues the boot-up with the default settings. The battery should be silver colored and about the size of a nickel. (You'll need to open the case of course.)
Solution 2: If it's not the battery you may have a BIOS problem. Sometimes you can try to correct it by selecting the 'reset configuration data' in CMOS.
IMPORTANT:Modifying BIOS/complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting
from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk.
Solution 3: If the issue persists, I would also suggest contacting the computer / laptop manufacturer for additional support and verify if they have any updates on this issue and if they can help to fix the same.
Let me know if that does or does not work. Good luck!
Hope this is helpful.
Thanks and Regards,
Vijay K - Microsoft Support
Visit our Microsoft Answers Feedback Forum and let us know what you think.
[If this post helps to resolve your issue, please click the "Mark as Answer" or "Helpful" button at the top of this message. By marking a post as Answered, or Helpful you help others find the answer faster.]