This article is from the VW Technical FAQ, by with numerous contributions by Jan Vandenbrande others.
A: If the crack is small (<2 cm in diameter) and either out of your line of
site or away from the wipers, you could have it filled
with an epoxy compound. Some have reported good luck with this, I have
not been very lucky.
If the windshield starts cracking, you could try to drill a hole to
stop the crack with a tungsten carbide drill bit, bit in all likelyhood
it's not going to do much good. You still need a new windshield.
I personally do not like the majority of aftermarket windshields.
They are either weaker (crack much quicker), show distortions, introduce
more wind noise, cause water leakage and therefore
I usually get the windshield at VW or order the OEM windshield
(Securit). They are more but I think they work better and seem to
hold up better to stone chips.
You may have to fight it with your insurance co though. I tell them
that the aftermarket windshields are not E2 certified and therefore
do not meet OEM specs.
The windshield on older VWs are just held in place with the rubber
molding, while the newer VWs have bonded windshields with a substantial
higher installation cost.
As always, you should replace *ALL* old seals when replacing a windshield,
it's worth the extra cost to avoid leaks and rust.
Look for a reputable place to install the
windshield because in the newer cars the windshield is part of the
structural integrity of the car.
Some of the mass market and cheaper place DO NOT BOND THE WINDSHIELD
ADEQUATELY. All they use is Butyl Tape, which stays soft and will
pop out the windshield in the event of a roll-over. Windshields Of America
lost a multimillion dollar law suit in Colorado because of this
(I mention them because I am EXTREMELY dissatisfied with them as well:
It took them 4 tries to get it right, and I am not even sure they
used anything but butyl tape).
According to the place I now go to (I loose one windshield every couple
years) recommends P255FC Urethane for bonding the windshield.
It becomes very rigid and you cannot prick it with a pin after it cures,
while butil tapes feels soft and goo-y.
 
Continue to: