Old PC/laptop dismantling

Solution 1:

Inside most is some type of whitish silver powdery putty

That is Thermal Paste:

Thermal paste consists of a polymerizable liquid matrix and large volume fractions of electrically insulating, but thermally conductive filler. Typical matrix materials are epoxies, silicones (Silicone grease), urethanes, and acrylates; solvent-based systems, hot-melt adhesives, and pressure-sensitive adhesive tapes are also available. Aluminum oxide, boron nitride, zinc oxide, and increasingly aluminum nitride are used as fillers for these types of adhesives. The filler loading can be as high as 70–80% by mass,

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The most effective (and most expensive) pastes consist almost entirely of liquid metal, usually a variation of the alloy galinstan

Source: Thermal paste - Wikipedia

Is it toxic?

Here is part of the the Safety Data sheet for Arctic Silver (a commonly used thermal paste):

• Hazard statements

  Causes eye irritation.

  Toxic to aquatic life with long lasting effects.

• Precautionary statements

  Avoid release to the environment.

  Wash thoroughly after handling.

  If in eyes: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do.

  Continue rinsing.

  If eye irritation persists: Get medical advice/attention.

  Collect spillage.

  Dispose of contents/container in accordance with local/regional/national/international regulations.

• Unknown acute toxicity:

  10 percent of the mixture consists of ingredient(s) of unknown toxicity

Source: AS5_SDS.pdf

How can I remove it?

Remove any thermal pads or other interface material from the heatsink.

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Thermal pads can be scraped off with a plastic tool that will not scratch the heatsink then the remnants can be removed with a xylene based cleaner, (Goof Off and some carburetor cleaners) acetone, mineral spirits, or 99% isopropyl alcohol.

Never use any oil or petroleum based cleaners (WD-40, citrus based cleaners and many automotive degreasers) on the base of a heatsink.

Source: Microsoft Word - Thermal Compound Instructions2.doc - Compound Instructions.pdf