Buying Crucial Brand Memory from Ebay Is it worth the risks

I need to upgrade my Dell Pc 4550 Fsb 533mhz purchased Jan 2003 with an extra 1 GB RAM (256Ram installed currently)

and my Packard Bell Laptop R 8750 12 months old by 1 GB RAM too (512Ram installed currently)

Is buying from Ebay worth it could I wreck my Pc by installing substand memory thats buttuming I am sold Counterfeits or Fakes which I am told have poor quality rating?

The seller on ebay has 100% feedback and is a powerseller.

I realise I will not have a 12 month gaurantee if I buy on ebay too. **************************************************************************************************** Heres what Crucial UK will be charging me

Remove Part No. CT563555 512MB, 184-pin DIMM Upgrade for a Dell Dimension 4550 (533MHz FSB) System £37.99 Quanbreasty 2 £75.98

Remove Part No. CT6464X335 512MB, 200-pin SODIMM Quanbreasty 2 £37.99 £75.98

Subtotal £151.96

Shipping Charge £5.00

VAT calculated at 21% for Ireland: £32.96

Estimated Total £189.92 (UK Sterling Currency) (Click to recalculate basket if changes are made.)

Any suggestions? has anyone on here purchased memory on Ebay and been happy? I keep getting windows crashing intermitently despite having fast dsl broadband 2megs per second what can I do besides upgrading extra memory to improve pc performance.

I was told by Crucial USA that the average system ram to have in a computer is 2 GB this seems like a mbuttive amount was he just saying this to increase sales of the Memory he was selling:)?

Regards

Sandra