What type of internet connection do you have? Broadband? Dial-up? Something else? Are you connecting wirelessly or do you have a wired connection?
Have you installed the latest Service Pack for Vista? If not, please do.
If you've got a broadband connection, have you tried re-initializing the modem/router like this?
Turn OFF the computer, then turn OFF the router, then turn OFF the modem (if they're separate routers and modems), then wait ten minutes.. Now turn ON the modem, wait two minutes for it to reinitialize, then turn ON the router (if they're separate), wait two more minutes, then turn ON the computer.
And because it could be a malware infection, please try the steps below:
On a friend or family member's computer, download the Malwarebytes installer and update files from the links below, copy them to a CD or flash drive, then transfer the files to the problem machine and use them. If you can't start the computer into "normal" windows, try installing, updating, and running the scans AFTER the computer is started into Safe Mode.. I use the sites below to download the installer file and the manual updater:
Once downloaded and before transferring them to the problem machine, rename the program installer "mbam-setup.exe" file to something else like "Gogetum.exe", then copy the installer file and the update file to a CD or flash drive.. Transfer the file to the problem machine, then install the "Gogetum.exe" file, then run the update to get the program current.. After that, run a full system scan and delete anything it finds.
Malwarebytes Installer Download Link (Clicking on the links below will immediately start the download dialogue window.)
Malwarebytes Manual Updater link
Next, download the SuperAntispyware program and the manual updater from the links below. After running the Malwarebytes tool above, if you still can't download and install it directly from the problem machine, download it on a friend or family member's computer as well. After installing and updating SuperAntispyware, run another full system scan and delete everything it finds as well. As before, you may need to rename the installer file to get the program to install.:
SuperAntispyware Manual Updater
In a few situations, in order for the program to run, it was also necessary to rename the main "mbam.exe" file also after installing it.. It resides in the C:\Programs Files\Malwarebytes Antimalware folder....
Hope this helps.