BSOD several times a day...

Did you reboot after you uninstalled the software associated with 1serial.sys?

Let's try this -

follow these instructions for enabling driver verifier: Using Driver Verifier to identify issues with Drivers
Please follow these instructions in order to run it:

Using Driver Verifier is an iffy proposition. Most times it'll crash and it'll tell you what the driver is. But sometimes it'll crash and won't tell you the driver. Other times it'll crash before you can log in to Windows. If you can't get to Safe Mode, then you'll have to resort to offline editing of the registry to disable Driver Verifier.

So, I'd suggest that you first backup your stuff and then make sure you've got access to another computer so you can contact us if problems arise. Then make a System Restore point (so you can restore the system using the Vista/Windows 7 Startup Repair feature).

Then, here's the procedure:
- Go to Start and type in "verifier" (without the quotes) and press Enter
- Select "Create custom settings (for code developers)" and click "Next"
- Select "Select individual settings from a full list" and click "Next"
- Select everything EXCEPT FOR "Low Resource Simulation" and click "Next"
- Select "Select driver names from a list" and click "Next"
Then select all drivers NOT provided by Microsoft and click "Next"
- Select "Finish" on the next page.

Reboot the system and wait for it to crash to the Blue Screen. Continue to use your system normally, and if you know what causes the crash, do that repeatedly. The objective here is to get the system to crash because Driver Verifier is stressing the drivers out. If it doesn't crash for you, then let it run for at least 36 hours of continuous operation (an estimate on my part).

Reboot into Windows (after the crash) and turn off Driver Verifier by going back in and selecting "Delete existing settings" on the first page, then locate and zip up the memory dump file and upload it with your next post.

If you can't get into Windows because it crashes too soon, try it in Safe Mode.
If you can't get into Safe Mode, try using System Restore from your installation DVD to set the system back to the previous restore point that you created.
If that doesn't work, post back and we'll have to see about fixing the registry entry off-line.

More info on this at this link: Using Driver Verifier to identify issues with Windows drivers for advanced users

Very good. Are you still getting BSOD's?

Time for a repair install: Repair Install