Why do you need to know?? Is there a problem with the windows?? The should be a sticker on the edge of the sashes, where it meets the frame. Most windows have a ten yr warranty on components and a 20 yr warranty on glass seal failure. If Lowes sold them, they either know where to send you, or they honor the warranty.
This is why I constantly harp on NOT buying windows from big box. What do you think manufacturers are trying to hide when they are afraid to put their name on their products.
Many vinyl window companies put a paper sticker on the exterior of the frame to identify the job. You would need to remove the window from the opening to see it.
As Bill said, they need to know who manufactured the window. If the local store can't help you, contact the main office. For them to say they don't know who they dealt with 10 years ago is ludicrous.
Look inside the head jamb. That is probably the most common location for a warranty sticker to be located. 20/10 warranties are typically on wood products, even cheapo vinyl (like the stuff at Lowes) should have a better warranty than that, possibly lifetime.
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