I might be shooting myself in the foot professionally by writing this entry, but I feel like the number of people reading this blog before they call me has got to be pretty slim. With that in mind, here are a few steps to take before calling a computer repair guy like myself:
If your computer's acting weird and you suspect you have a virus:
1. Install Malware Bytes (malwarebytes.org), let it update fully, then run a full scan. It's free and they catch a LOT of new viruses.
2. Install SuperAntiSpyware (superantispyware.com), update it, then run a full scan. Also free, also good.
3. Run GMER (www.gmer.net). If anything pops up in RED TEXT then you have a rootkit infection. Do the safe mode thing below and run the virus scans again.
If those things don't work or don't help, try doing them from Safe Mode.
How to get into Safe Mode:
1. Reboot the computer. Just after the initial loading screen and before the windows logo comes up, start tapping the F8 key on your keyboard repeatedly. If you see the windows logo you've missed your chance, reboot and try again and start tapping F8 sooner.
2. If you did it right, you'll see a diagnostics menu with an option for "Safe Mode" on it. Choose "Safe Mode with Networking".
3. Perform the steps above again.
If your computer is no longer booting all the way into windows:
If you're still seeing the windows logo for a brief amount of time before your computer crashes or reboots, there's hope!
1. Boot into Safe Mode like I described above.
2. Run a disk scan by clicking on the "start" button, clicking on "run", and typing in "chkdsk /f". If you see a black window that's fine, just say "yes" if it asks you if you want to run a scan on reboot.
3. Reboot your computer.
If it's still broke:
1. Boot into Safe Mode like I described above.
2. Open MSConfig by clicking on the "start" button, clicking on
"run", and typing in "msconfig". Choose "System Restore" from the tools menu.

Click "Launch". Follow the prompts and choose a date from a few days ago to restore from. This will sometimes fix the problem as well.
if it's STILL broke:
1. Remove any new hardware you've installed.
2. Boot into Safe Mode and click on the "start" button, then click on "control panel"
3. Click on "add/remove programs"
4. Remove any new programs you've installed.
5. Install the virus scanners metnioned above and run scans.
Hope that helps! See you next time.