I am running Windows XP Home. Install was clean on a brand new HDD. I just purchased an APC UPS Backups Pro 1100. Comes with the PowerChute Software and Serial Cable. Hooked up the Serial Cable to my Serial Port (only have 1 serial port) and tried to use the WinXP UPS Service to monitor the UPS. Unfortunately, I get the following: "The UPS Service has lost communication with the UPS." In the Device Manager the Serial Port shows up without Conflicts. Port is set to COM1 / IRQ4. I have gone into the BIOS and changed Serial Port from AUTO to Enabled and verified Memory Settings and IRQ. Nothing. I have changed the Properties of the Port inside of XP to the minimum and it still will not work. I also updated my BIOS to the most current version available from DELL. I have removed the Port, disabled my internal Modem (COM3) and tried pretty much everything I can think of. I do have a PPC connected via USB. The ActiveSync settings were checked to use the Serial Port and a conflict did occur on bootup with ActiveSync. It was like ActiveSync knew the port was in use and I had to turn that option off in AS. I also hooked up my iPaq via the Serial Port and tried to use ActiveSync. It recognized a device was connected, but could sync. I get the impression that the port is working, but it is almost like it is only going one way. Like any BiDirectional Communication is not working. Sorry for the lengthy post, but I wanted to try and be as thorough as possible. Any help would be greatly appreciated. **EDIT** I would also like to add that I downloaded the most current software from APC's website and tried installing it. When it gets to the point of detecting the UPS the PowerChute software also fails.