There are three question in our mind.
1. How many pages, we will get for Word or Letter in Google Search ?
2. How Google Search response to Regex ?
3. How many pages Google Search has archived or Indexed (Some what nearer numbers would be fine) ?
We will start with first question.
For word 'Linux' we got... Results 1 - 10 of about 331,000,000 for Linux [definition]. (0.27 seconds) For word 'Google' we got... Results 1 - 10 of about 561,000,000 for Windows [definition]. (0.04 seconds) For word 'Windows' we got... Results 1 - 10 of about 691,000,000 for Google. (0.05 seconds) Finally 'We' we got (Yes 'We', Go, ahead, you will find, Why 'We'?)