Technically doing anything inside the machine invalidates the warranty
Whoa! That is NOT true! Those warranty void stickers mean nothing! Users have the Right
to open the side of "their" case, upgrade RAM, add a drive, new fan, or swap out video cards. More importantly, they have the responsibility
to keep the interior of their cases clean
of heat trapping dust and dirt. PC makers can put stickers everywhere, it does not matter! As long as there are "user serviceable" parts inside, you have the right, as a consumer, to open it up, and do whatever maintenance you need to do - as long as it is done correctly
. Computers have fans that constantly suck dust, dirt, and hair inside. Users MUST, as a "user responsibility", open the case to inspect (I recommend monthly) and clean as necessary. No warranty covers damage due to heat buildup as the result of user neglect!
If there are no user serviceable parts inside a device, such as the interior of a hard drive for example, then breaking the seal and opening the hard drive case might void the warranty on the hard drive - this is because hard drives are sealed to keep dust out. Damage may result just by breaking the dust seal, and exposing the platters to contaminants. But there are many user serviceable parts inside a PC.
Understand that most independent PC assemblers, including yours truly, feel those stickers are nothing more than a scam to coerce and scare owners in to having all maintenance, including upgrade purchases, done through them. Consumer protection laws protect us from such abuse. Automobile makers tried the same thing and were shot down long ago. You can do all the maintenance (routine and otherwise) in your own backyard, as long as you do it correctly, using any oil and parts that meet industry standards, and not void your warranty (just keep good records and receipts for supplies). The big electronics firms tried that with TVs - yet tube testers were in every drug, grocery, and hardware store because we had the right to break the seal, remove the back, pull the tubes, and take them for testing.
So if someone says you broke the seal, the warranty is void, remind them it is your machine, your right and you will gladly meet them in court if they choose. Since they know they will lose, and get stuck with your legal fees too, they will honor it.