My mother's computer, a Compaq cq5110f, has been having a problem with waking from sleep mode. It started after I installed some windows updates, and installed Avast free edition. I'll put the computer to sleep, and I'll be able to wake it up if I try soon after sleeping it. If I wait a little while longer, the power LED will switch from orange to blue (indicating it's coming back from sleep mode), and I'll hear the fans start up, but the monitor wont come back. I've tried using a different monitor, but the same result ensues. I've tried different fixes online, but nothing as worked. I've even done a system restore to before I installed the updates and the Avast, but the problem still persists. Any ideas?
Read this: http://gsmblog.com/post/Difference-between-S1-(POS)-and-S3-(STR)-standby-mode-in-BIOS.aspx.
It explains the different sleep modes available in your BIOS settings.
S4 is the safest if your system supports this mode. S3 is faster at waking but, if the power fails and you are not using a battery backup you will loose all unsaved data.
What OS are you using?