Every now and then when I boot up and login to my machine I will be taken to the default screen on Windows 7 (Blue fish background, default theme, etc...). 97% of the time I am taken to my regular desktop (My Background, black theme, etc...).
I can't remember if Vista did this but I know Vista did warn me that my HDD was failing. I thought it was because I dual-booted with Ubuntu.
So is my HDD failing or is it just Windows and Ubuntu refusing to play nicely together on the same HDD?
It is possible Windows 7 isn't able to read your profile during those occasions when it shows you the default screen.
This in turn might be due to issues with reading certain HDD sectors. I'd advice you to check your HDD's health as nik suggests.
I'm assuming you have Windows and Ubuntu dual-boot, and if so, I don't see why that would cause Windows 7 to boot into the default screen sometimes.
Ubuntu provides a smartmontools package to check any modern ATA/SCSI drive that supports the Self-Monitoring, Analysis and Reporting Technology System (SMART).
Install this smartmontools package
sudo apt-get install smartmontools
View the information provided by smartctl for your drive (assuming /dev/sda)
sudo smartctl -a /dev/sda
Run a self-test on the drive
sudo smartctl -t long /dev/sda
View the result of the selftest
sudo smartctl -l selftest /dev/sda
Before you start the diagnosis, have a quick look through the fairly extensive man page provided for smartctl. You can choose to customize the verbosity and error-tolerance of the tool.
You can also check the disk using badblocks. However, be careful of two issues:
sudo badblocks -nvs /dev/sda
You could use a Hard Disk Utility like HDTune to analyze your hard disk once.
I do not suspect your HDD yet, but HDTune is good to keep handy for regular checks.
