Please note that CPU upgrades in notebooks/laptops/netbooks are highly problematic because they depend on often uncertain motherboard specifications (different notebook models bearing the same series number in your question can have different internal and external specification and be based on different motherboards).
The most serious problem you face is that CPU upgrades in laptops/notebooks/netbooks inevitably require near complete disassembly and the correct reassembly of the computer. Inevitably, this type of work is best done by an experienced professional, trained for and capable of performing a warrantied repair. Understandably, the associated labor costs will be on the high side.
Also, upgrading the CPU requires the user to first risk expenditure on an item that cannot be returned to the seller or supplier if later found to be incompatible but could still be a potentially expensive replacement product, without being absolutely certain that is compatible with the motherboard for which it is intended.
So you will need to do extensive research on the specification of the precise motherboard of the precise model of your notebook. To do this, you will need the full, long, specific model number plus also the Serial Number (S/N) and Part Number (P/N) of the computer that are usually printed on a label underneath the computer. From these, you should obtain the P/N of the motherboard, then navigate to the support and product information pages of the motherboard manufacturer's website to verify the CPU compatibility specifications of the motherboard and then proceed from there.
Intel Pentium Mobile processor T4200 (1 MB L2 cache, 2 GHz, 800 MHz FSB, 35 W), or T3400 (1 MB L2 Cache, 2.16 GHz, 667 MHz FSB, 35 W), supporting Intel 64 architecture
Your notebook features the above Central Processing Unit (CPU) in its standard specification, according to Acer. This CPU is commonly referred to as a Dual Core / Intel Pentium M / 2.2GHz / 64 Bit Processor. This type and Model of Processor is outdated and the upgrade options available to you are limited.
The indications are that your best course of action would be to back up any important data stored on this notebook's Hard Disk Drive (HDD), restore the notebook to Factory Settings, sell it on eBay or CraigsList or any similar website popular, in your geographical location, for the buying and selling of Used Consumer Goods and then put any sale income raised towards a new, state-of-the-art notebook capable of performing the function(s) in which the current notebook is disappointing you and steering you towards radical thoughts such as CPU upgrades.
At the very least, consider several or all of the far easier, far cheaper and far less labor-intensive and labor-expensive upgrade options to improve the power, speed and performance of this notebook before contemplating a CPU Upgrade, such as, a Maximum Capacity RAM Upgrade, an Operating System (O/S) Upgrade, upgrading to a higher performance, higher Spin Speed and/or higher capacity HDD or newer technology Solid State Drive (SSD).
Your full notebook specification and CPU Upgrade Options can be found on the support pages of the official Acer and Intel websites below:http://support.acer.com/acerpanam/notebook/2010/acer/aspire/aspire4736z/aspire4736zsp2.shtmlhttp://www.intel.com/en_uk/consumer/products/processors/compare-processors.htm?fam=corei5http://www.intel.com/en_uk/consumer/products/processors/compare-processors.htm?fam=corei5