If it won't let you enter, hold 'f8' key after booting to 'starting winblows bla bla', for step by stem confirmation. approve only 'himem.sys' and deny all others by typing 'n' for them. Type 'scanreg' at DOS prompt. Then type '/restore'. Select the last troubble free backup you are aware of - all spamware is now gone

You can go back in and append a text message to the offending (corrupt and virus/spamware/hijack ridden' registry by typing '*/comment=<text>*' to putyour message in there. You can say something like 'infected' to note not to use this backup, or delete it, etc.
I am new to this trick but it is by design. There seem to be a variety of so-called 'software' companies out there now charging a bunch of money just to activate this feature via a shell that hides the fact it is already a FREE part of winblows already!

All hail Bill Gates!

Thank U Bill! They always said Winblows is all U need - in some ways that seems 2 B true.